diff --git a/cmd/protoc-gen-go/main.go b/cmd/protoc-gen-go/main.go
index a03ae36..0c1b119 100644
--- a/cmd/protoc-gen-go/main.go
+++ b/cmd/protoc-gen-go/main.go
@@ -56,6 +56,7 @@
 	descriptorVar string // var containing the gzipped FileDescriptorProto
 	allEnums      []*protogen.Enum
 	allMessages   []*protogen.Message
+	allExtensions []*protogen.Extension
 }
 
 func genFile(gen *protogen.Plugin, file *protogen.File) {
@@ -68,11 +69,19 @@
 		f.locationMap[key] = append(f.locationMap[key], loc)
 	}
 
+	// The different order for enums and extensions is to match the output
+	// of the previous implementation.
+	//
+	// TODO: Eventually make this consistent.
 	f.allEnums = append(f.allEnums, f.File.Enums...)
-	f.allMessages = append(f.allMessages, f.File.Messages...)
 	for _, message := range f.Messages {
-		f.initMessage(message)
+		walkMessage(message, func(message *protogen.Message) {
+			f.allMessages = append(f.allMessages, message)
+			f.allEnums = append(f.allEnums, message.Enums...)
+			f.allExtensions = append(f.allExtensions, message.Extensions...)
+		})
 	}
+	f.allExtensions = append(f.allExtensions, f.File.Extensions...)
 
 	// Determine the name of the var holding the file descriptor:
 	//
@@ -120,17 +129,20 @@
 	for _, message := range f.allMessages {
 		genMessage(gen, g, f, message)
 	}
+	for _, extension := range f.Extensions {
+		genExtension(gen, g, f, extension)
+	}
 
 	genInitFunction(gen, g, f)
 
 	genFileDescriptor(gen, g, f)
 }
 
-func (f *File) initMessage(message *protogen.Message) {
-	f.allEnums = append(f.allEnums, message.Enums...)
-	f.allMessages = append(f.allMessages, message.Messages...)
+// walkMessage calls f on message and all of its descendants.
+func walkMessage(message *protogen.Message, f func(*protogen.Message)) {
+	f(message)
 	for _, m := range message.Messages {
-		f.initMessage(m)
+		walkMessage(m, f)
 	}
 }
 
@@ -300,6 +312,18 @@
 		g.P(field.GoName, " ", goType, " `", strings.Join(tags, " "), "`")
 	}
 	g.P("XXX_NoUnkeyedLiteral struct{} `json:\"-\"`")
+
+	if message.Desc.ExtensionRanges().Len() > 0 {
+		var tags []string
+		if messageOptions(gen, message).GetMessageSetWireFormat() {
+			tags = append(tags, `protobuf_messageset:"1"`)
+		}
+		tags = append(tags, `json:"-"`)
+		g.P(protogen.GoIdent{
+			GoImportPath: protoPackage,
+			GoName:       "XXX_InternalExtensions",
+		}, " `", strings.Join(tags, " "), "`")
+	}
 	// TODO XXX_InternalExtensions
 	g.P("XXX_unrecognized []byte `json:\"-\"`")
 	g.P("XXX_sizecache int32 `json:\"-\"`")
@@ -323,7 +347,43 @@
 	g.P("func (*", message.GoIdent, ") Descriptor() ([]byte, []int) {")
 	g.P("return ", f.descriptorVar, ", []int{", strings.Join(indexes, ","), "}")
 	g.P("}")
-	// TODO: extension support methods
+	g.P()
+
+	// ExtensionRangeArray
+	if extranges := message.Desc.ExtensionRanges(); extranges.Len() > 0 {
+		if messageOptions(gen, message).GetMessageSetWireFormat() {
+			g.P("func (m *", message.GoIdent, ") MarshalJSON() ([]byte, error) {")
+			g.P("return ", protogen.GoIdent{
+				GoImportPath: protoPackage,
+				GoName:       "MarshalMessageSetJSON",
+			}, "(&m.XXX_InternalExtensions)")
+			g.P("}")
+			g.P("func (m *", message.GoIdent, ") UnmarshalJSON(buf []byte) error {")
+			g.P("return ", protogen.GoIdent{
+				GoImportPath: protoPackage,
+				GoName:       "UnmarshalMessageSetJSON",
+			}, "(buf, &m.XXX_InternalExtensions)")
+			g.P("}")
+			g.P()
+		}
+
+		protoExtRange := protogen.GoIdent{
+			GoImportPath: protoPackage,
+			GoName:       "ExtensionRange",
+		}
+		extRangeVar := "extRange_" + message.GoIdent.GoName
+		g.P("var ", extRangeVar, " = []", protoExtRange, " {")
+		for i := 0; i < extranges.Len(); i++ {
+			r := extranges.Get(i)
+			g.P("{Start:", r[0], ", End:", r[1]-1 /* inclusive */, "},")
+		}
+		g.P("}")
+		g.P()
+		g.P("func (*", message.GoIdent, ") ExtensionRangeArray() []", protoExtRange, " {")
+		g.P("return ", extRangeVar)
+		g.P("}")
+		g.P()
+	}
 
 	// Table-driven proto support.
 	//
@@ -449,6 +509,9 @@
 	if len(message.Oneofs) > 0 {
 		genOneofFuncs(gen, g, f, message)
 	}
+	for _, extension := range message.Extensions {
+		genExtension(gen, g, f, extension)
+	}
 }
 
 // fieldGoType returns the Go type used for a field.
@@ -621,10 +684,42 @@
 	return string(field.Desc.Name()) + ",omitempty"
 }
 
+func genExtension(gen *protogen.Plugin, g *protogen.GeneratedFile, f *File, extension *protogen.Extension) {
+	g.P("var ", extensionVar(f, extension), " = &", protogen.GoIdent{
+		GoImportPath: protoPackage,
+		GoName:       "ExtensionDesc",
+	}, "{")
+	g.P("ExtendedType: (*", extension.ExtendedType.GoIdent, ")(nil),")
+	goType, pointer := fieldGoType(g, extension)
+	if pointer {
+		goType = "*" + goType
+	}
+	g.P("ExtensionType: (", goType, ")(nil),")
+	g.P("Field: ", extension.Desc.Number(), ",")
+	g.P("Name: ", strconv.Quote(string(extension.Desc.FullName())), ",")
+	g.P("Tag: ", strconv.Quote(fieldProtobufTag(extension)), ",")
+	g.P("Filename: ", strconv.Quote(f.Desc.Path()), ",")
+	g.P("}")
+	g.P()
+}
+
+// extensionVar returns the var holding the ExtensionDesc for an extension.
+func extensionVar(f *File, extension *protogen.Extension) protogen.GoIdent {
+	name := "E_"
+	if extension.ParentMessage != nil {
+		name += extension.ParentMessage.GoIdent.GoName + "_"
+	}
+	name += extension.GoName
+	return protogen.GoIdent{
+		GoImportPath: f.GoImportPath,
+		GoName:       name,
+	}
+}
+
 // genInitFunction generates an init function that registers the types in the
 // generated file with the proto package.
 func genInitFunction(gen *protogen.Plugin, g *protogen.GeneratedFile, f *File) {
-	if len(f.allMessages) == 0 && len(f.allEnums) == 0 {
+	if len(f.allMessages) == 0 && len(f.allEnums) == 0 && len(f.allExtensions) == 0 {
 		return
 	}
 
@@ -668,6 +763,12 @@
 			GoName:       "RegisterEnum",
 		}, fmt.Sprintf("(%q, %s_name, %s_value)", enumRegistryName(enum), name, name))
 	}
+	for _, extension := range f.allExtensions {
+		g.P(protogen.GoIdent{
+			GoImportPath: protoPackage,
+			GoName:       "RegisterExtension",
+		}, "(", extensionVar(f, extension), ")")
+	}
 	g.P("}")
 	g.P()
 }
diff --git a/cmd/protoc-gen-go/oneof.go b/cmd/protoc-gen-go/oneof.go
index fa90b1a..98880ec 100644
--- a/cmd/protoc-gen-go/oneof.go
+++ b/cmd/protoc-gen-go/oneof.go
@@ -340,7 +340,7 @@
 // fieldOneofType returns the wrapper type used to represent a field in a oneof.
 func fieldOneofType(field *protogen.Field) protogen.GoIdent {
 	return protogen.GoIdent{
-		GoImportPath: field.ContainingType.GoIdent.GoImportPath,
-		GoName:       field.ContainingType.GoIdent.GoName + "_" + field.GoName,
+		GoImportPath: field.ParentMessage.GoIdent.GoImportPath,
+		GoName:       field.ParentMessage.GoIdent.GoName + "_" + field.GoName,
 	}
 }
diff --git a/cmd/protoc-gen-go/options.go b/cmd/protoc-gen-go/options.go
new file mode 100644
index 0000000..a3828ea
--- /dev/null
+++ b/cmd/protoc-gen-go/options.go
@@ -0,0 +1,41 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains functions for fetching the options for a protoreflect descriptor.
+//
+// TODO: Replace this with the appropriate protoreflect API, once it exists.
+
+package main
+
+import (
+	descpb "github.com/golang/protobuf/protoc-gen-go/descriptor"
+	"google.golang.org/proto/protogen"
+	"google.golang.org/proto/reflect/protoreflect"
+)
+
+// messageOptions returns the MessageOptions for a message.
+func messageOptions(gen *protogen.Plugin, message *protogen.Message) *descpb.MessageOptions {
+	file, ok := descriptorFile(gen, message.Desc)
+	if !ok {
+		return nil
+	}
+	desc := file.Proto.MessageType[message.Path[1]]
+	for i := 3; i < len(message.Path); i += 2 {
+		desc = desc.NestedType[message.Path[1]]
+	}
+	return desc.GetOptions()
+}
+
+func descriptorFile(gen *protogen.Plugin, desc protoreflect.Descriptor) (*protogen.File, bool) {
+	for {
+		if fdesc, ok := desc.(protoreflect.FileDescriptor); ok {
+			return gen.FileByName(fdesc.Path())
+		}
+		var ok bool
+		desc, ok = desc.Parent()
+		if !ok {
+			return nil, false
+		}
+	}
+}
diff --git a/cmd/protoc-gen-go/testdata/comments/comments.pb.go b/cmd/protoc-gen-go/testdata/comments/comments.pb.go
index 22046f4..682a960 100644
--- a/cmd/protoc-gen-go/testdata/comments/comments.pb.go
+++ b/cmd/protoc-gen-go/testdata/comments/comments.pb.go
@@ -35,6 +35,7 @@
 func (*Message1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_885e8293f1fab554, []int{0}
 }
+
 func (m *Message1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message1.Unmarshal(m, b)
 }
@@ -53,37 +54,6 @@
 
 var xxx_messageInfo_Message1 proto.InternalMessageInfo
 
-// COMMENT: Message2
-type Message2 struct {
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
-
-func (m *Message2) Reset()         { *m = Message2{} }
-func (m *Message2) String() string { return proto.CompactTextString(m) }
-func (*Message2) ProtoMessage()    {}
-func (*Message2) Descriptor() ([]byte, []int) {
-	return fileDescriptor_885e8293f1fab554, []int{1}
-}
-func (m *Message2) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_Message2.Unmarshal(m, b)
-}
-func (m *Message2) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_Message2.Marshal(b, m, deterministic)
-}
-func (m *Message2) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_Message2.Merge(m, src)
-}
-func (m *Message2) XXX_Size() int {
-	return xxx_messageInfo_Message2.Size(m)
-}
-func (m *Message2) XXX_DiscardUnknown() {
-	xxx_messageInfo_Message2.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_Message2 proto.InternalMessageInfo
-
 // COMMENT: Message1A
 type Message1_Message1A struct {
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
@@ -97,6 +67,7 @@
 func (*Message1_Message1A) Descriptor() ([]byte, []int) {
 	return fileDescriptor_885e8293f1fab554, []int{0, 0}
 }
+
 func (m *Message1_Message1A) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message1_Message1A.Unmarshal(m, b)
 }
@@ -128,6 +99,7 @@
 func (*Message1_Message1B) Descriptor() ([]byte, []int) {
 	return fileDescriptor_885e8293f1fab554, []int{0, 1}
 }
+
 func (m *Message1_Message1B) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message1_Message1B.Unmarshal(m, b)
 }
@@ -146,6 +118,38 @@
 
 var xxx_messageInfo_Message1_Message1B proto.InternalMessageInfo
 
+// COMMENT: Message2
+type Message2 struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Message2) Reset()         { *m = Message2{} }
+func (m *Message2) String() string { return proto.CompactTextString(m) }
+func (*Message2) ProtoMessage()    {}
+func (*Message2) Descriptor() ([]byte, []int) {
+	return fileDescriptor_885e8293f1fab554, []int{1}
+}
+
+func (m *Message2) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Message2.Unmarshal(m, b)
+}
+func (m *Message2) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Message2.Marshal(b, m, deterministic)
+}
+func (m *Message2) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Message2.Merge(m, src)
+}
+func (m *Message2) XXX_Size() int {
+	return xxx_messageInfo_Message2.Size(m)
+}
+func (m *Message2) XXX_DiscardUnknown() {
+	xxx_messageInfo_Message2.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Message2 proto.InternalMessageInfo
+
 // COMMENT: Message2A
 type Message2_Message2A struct {
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
@@ -159,6 +163,7 @@
 func (*Message2_Message2A) Descriptor() ([]byte, []int) {
 	return fileDescriptor_885e8293f1fab554, []int{1, 0}
 }
+
 func (m *Message2_Message2A) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message2_Message2A.Unmarshal(m, b)
 }
@@ -190,6 +195,7 @@
 func (*Message2_Message2B) Descriptor() ([]byte, []int) {
 	return fileDescriptor_885e8293f1fab554, []int{1, 1}
 }
+
 func (m *Message2_Message2B) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message2_Message2B.Unmarshal(m, b)
 }
@@ -210,9 +216,9 @@
 
 func init() {
 	proto.RegisterType((*Message1)(nil), "goproto.protoc.proto2.Message1")
-	proto.RegisterType((*Message2)(nil), "goproto.protoc.proto2.Message2")
 	proto.RegisterType((*Message1_Message1A)(nil), "goproto.protoc.proto2.Message1.Message1A")
 	proto.RegisterType((*Message1_Message1B)(nil), "goproto.protoc.proto2.Message1.Message1B")
+	proto.RegisterType((*Message2)(nil), "goproto.protoc.proto2.Message2")
 	proto.RegisterType((*Message2_Message2A)(nil), "goproto.protoc.proto2.Message2.Message2A")
 	proto.RegisterType((*Message2_Message2B)(nil), "goproto.protoc.proto2.Message2.Message2B")
 }
diff --git a/cmd/protoc-gen-go/testdata/extensions/base/base.pb.go b/cmd/protoc-gen-go/testdata/extensions/base/base.pb.go
new file mode 100644
index 0000000..8bbe3f2
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/base/base.pb.go
@@ -0,0 +1,141 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: extensions/base/base.proto
+
+package base
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type BaseMessage struct {
+	Field                        *string  `protobuf:"bytes,1,opt,name=field" json:"field,omitempty"`
+	XXX_NoUnkeyedLiteral         struct{} `json:"-"`
+	proto.XXX_InternalExtensions `json:"-"`
+	XXX_unrecognized             []byte `json:"-"`
+	XXX_sizecache                int32  `json:"-"`
+}
+
+func (m *BaseMessage) Reset()         { *m = BaseMessage{} }
+func (m *BaseMessage) String() string { return proto.CompactTextString(m) }
+func (*BaseMessage) ProtoMessage()    {}
+func (*BaseMessage) Descriptor() ([]byte, []int) {
+	return fileDescriptor_aebb28f8d5a04466, []int{0}
+}
+
+var extRange_BaseMessage = []proto.ExtensionRange{
+	{Start: 4, End: 9},
+	{Start: 16, End: 536870911},
+}
+
+func (*BaseMessage) ExtensionRangeArray() []proto.ExtensionRange {
+	return extRange_BaseMessage
+}
+
+func (m *BaseMessage) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_BaseMessage.Unmarshal(m, b)
+}
+func (m *BaseMessage) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_BaseMessage.Marshal(b, m, deterministic)
+}
+func (m *BaseMessage) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_BaseMessage.Merge(m, src)
+}
+func (m *BaseMessage) XXX_Size() int {
+	return xxx_messageInfo_BaseMessage.Size(m)
+}
+func (m *BaseMessage) XXX_DiscardUnknown() {
+	xxx_messageInfo_BaseMessage.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_BaseMessage proto.InternalMessageInfo
+
+func (m *BaseMessage) GetField() string {
+	if m != nil && m.Field != nil {
+		return *m.Field
+	}
+	return ""
+}
+
+type MessageSetWireFormatMessage struct {
+	XXX_NoUnkeyedLiteral         struct{} `json:"-"`
+	proto.XXX_InternalExtensions `protobuf_messageset:"1" json:"-"`
+	XXX_unrecognized             []byte `json:"-"`
+	XXX_sizecache                int32  `json:"-"`
+}
+
+func (m *MessageSetWireFormatMessage) Reset()         { *m = MessageSetWireFormatMessage{} }
+func (m *MessageSetWireFormatMessage) String() string { return proto.CompactTextString(m) }
+func (*MessageSetWireFormatMessage) ProtoMessage()    {}
+func (*MessageSetWireFormatMessage) Descriptor() ([]byte, []int) {
+	return fileDescriptor_aebb28f8d5a04466, []int{1}
+}
+
+func (m *MessageSetWireFormatMessage) MarshalJSON() ([]byte, error) {
+	return proto.MarshalMessageSetJSON(&m.XXX_InternalExtensions)
+}
+func (m *MessageSetWireFormatMessage) UnmarshalJSON(buf []byte) error {
+	return proto.UnmarshalMessageSetJSON(buf, &m.XXX_InternalExtensions)
+}
+
+var extRange_MessageSetWireFormatMessage = []proto.ExtensionRange{
+	{Start: 100, End: 2147483646},
+}
+
+func (*MessageSetWireFormatMessage) ExtensionRangeArray() []proto.ExtensionRange {
+	return extRange_MessageSetWireFormatMessage
+}
+
+func (m *MessageSetWireFormatMessage) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_MessageSetWireFormatMessage.Unmarshal(m, b)
+}
+func (m *MessageSetWireFormatMessage) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_MessageSetWireFormatMessage.Marshal(b, m, deterministic)
+}
+func (m *MessageSetWireFormatMessage) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_MessageSetWireFormatMessage.Merge(m, src)
+}
+func (m *MessageSetWireFormatMessage) XXX_Size() int {
+	return xxx_messageInfo_MessageSetWireFormatMessage.Size(m)
+}
+func (m *MessageSetWireFormatMessage) XXX_DiscardUnknown() {
+	xxx_messageInfo_MessageSetWireFormatMessage.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_MessageSetWireFormatMessage proto.InternalMessageInfo
+
+func init() {
+	proto.RegisterType((*BaseMessage)(nil), "goproto.protoc.extension.base.BaseMessage")
+	proto.RegisterType((*MessageSetWireFormatMessage)(nil), "goproto.protoc.extension.base.MessageSetWireFormatMessage")
+}
+
+func init() { proto.RegisterFile("extensions/base/base.proto", fileDescriptor_aebb28f8d5a04466) }
+
+var fileDescriptor_aebb28f8d5a04466 = []byte{
+	// 198 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x92, 0x4a, 0xad, 0x28, 0x49,
+	0xcd, 0x2b, 0xce, 0xcc, 0xcf, 0x2b, 0xd6, 0x4f, 0x4a, 0x2c, 0x4e, 0x05, 0x13, 0x7a, 0x05, 0x45,
+	0xf9, 0x25, 0xf9, 0x42, 0xb2, 0xe9, 0xf9, 0x60, 0x06, 0x84, 0x9b, 0xac, 0x07, 0x57, 0xaa, 0x07,
+	0x52, 0xa4, 0x64, 0xcc, 0xc5, 0xed, 0x94, 0x58, 0x9c, 0xea, 0x9b, 0x5a, 0x5c, 0x9c, 0x98, 0x9e,
+	0x2a, 0x24, 0xc2, 0xc5, 0x9a, 0x96, 0x99, 0x9a, 0x93, 0x22, 0xc1, 0xa8, 0xc0, 0xa8, 0xc1, 0x19,
+	0x04, 0xe1, 0x68, 0xb1, 0x70, 0xb0, 0x08, 0x70, 0x69, 0x71, 0x70, 0x08, 0x08, 0x34, 0x34, 0x34,
+	0x34, 0x30, 0x29, 0x69, 0x73, 0x49, 0x43, 0x35, 0x04, 0xa7, 0x96, 0x84, 0x67, 0x16, 0xa5, 0xba,
+	0xe5, 0x17, 0xe5, 0x26, 0x96, 0x40, 0xc5, 0xb4, 0x38, 0x38, 0x52, 0x04, 0xfe, 0xff, 0xff, 0xff,
+	0x9f, 0xdd, 0x8a, 0x89, 0x83, 0xd1, 0xc9, 0x25, 0xca, 0x29, 0x3d, 0x3f, 0x3f, 0x3d, 0x27, 0x55,
+	0x2f, 0x3d, 0x3f, 0x27, 0x31, 0x2f, 0x5d, 0x2f, 0xbf, 0x28, 0x5d, 0x1f, 0xec, 0x18, 0xfd, 0xe4,
+	0xdc, 0x14, 0x08, 0x2b, 0x59, 0x37, 0x3d, 0x35, 0x4f, 0x37, 0x3d, 0x5f, 0xbf, 0x24, 0xb5, 0xb8,
+	0x24, 0x25, 0xb1, 0x24, 0x51, 0x1f, 0xcd, 0x47, 0x80, 0x00, 0x00, 0x00, 0xff, 0xff, 0x5f, 0x09,
+	0xf0, 0xbd, 0xe3, 0x00, 0x00, 0x00,
+}
diff --git a/cmd/protoc-gen-go/testdata/extensions/base/base.proto b/cmd/protoc-gen-go/testdata/extensions/base/base.proto
new file mode 100644
index 0000000..3c16d25
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/base/base.proto
@@ -0,0 +1,20 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+syntax = "proto2";
+
+package goproto.protoc.extension.base;
+
+option go_package = "google.golang.org/proto/cmd/protoc-gen-go/testdata/extensions/base";
+
+message BaseMessage {
+  optional string field = 1;
+  extensions 4 to 9;
+  extensions 16 to max;
+}
+
+message MessageSetWireFormatMessage {
+  option message_set_wire_format = true;
+  extensions 100 to max;
+}
diff --git a/cmd/protoc-gen-go/testdata/extensions/ext/ext.pb.go b/cmd/protoc-gen-go/testdata/extensions/ext/ext.pb.go
new file mode 100644
index 0000000..b419842
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/ext/ext.pb.go
@@ -0,0 +1,866 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: extensions/ext/ext.proto
+
+package ext
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	base "google.golang.org/proto/cmd/protoc-gen-go/testdata/extensions/base"
+	extra "google.golang.org/proto/cmd/protoc-gen-go/testdata/extensions/extra"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type Enum int32
+
+const (
+	Enum_ZERO Enum = 0
+)
+
+var Enum_name = map[int32]string{
+	0: "ZERO",
+}
+
+var Enum_value = map[string]int32{
+	"ZERO": 0,
+}
+
+func (x Enum) Enum() *Enum {
+	p := new(Enum)
+	*p = x
+	return p
+}
+
+func (x Enum) String() string {
+	return proto.EnumName(Enum_name, int32(x))
+}
+
+func (x *Enum) UnmarshalJSON(data []byte) error {
+	value, err := proto.UnmarshalJSONEnum(Enum_value, data, "Enum")
+	if err != nil {
+		return err
+	}
+	*x = Enum(value)
+	return nil
+}
+
+func (Enum) EnumDescriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{0}
+}
+
+type Message struct {
+	Data                 []byte   `protobuf:"bytes,1,opt,name=data" json:"data,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Message) Reset()         { *m = Message{} }
+func (m *Message) String() string { return proto.CompactTextString(m) }
+func (*Message) ProtoMessage()    {}
+func (*Message) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{0}
+}
+
+func (m *Message) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Message.Unmarshal(m, b)
+}
+func (m *Message) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Message.Marshal(b, m, deterministic)
+}
+func (m *Message) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Message.Merge(m, src)
+}
+func (m *Message) XXX_Size() int {
+	return xxx_messageInfo_Message.Size(m)
+}
+func (m *Message) XXX_DiscardUnknown() {
+	xxx_messageInfo_Message.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Message proto.InternalMessageInfo
+
+func (m *Message) GetData() []byte {
+	if m != nil {
+		return m.Data
+	}
+	return nil
+}
+
+type Message_M struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Message_M) Reset()         { *m = Message_M{} }
+func (m *Message_M) String() string { return proto.CompactTextString(m) }
+func (*Message_M) ProtoMessage()    {}
+func (*Message_M) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{0, 0}
+}
+
+func (m *Message_M) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Message_M.Unmarshal(m, b)
+}
+func (m *Message_M) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Message_M.Marshal(b, m, deterministic)
+}
+func (m *Message_M) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Message_M.Merge(m, src)
+}
+func (m *Message_M) XXX_Size() int {
+	return xxx_messageInfo_Message_M.Size(m)
+}
+func (m *Message_M) XXX_DiscardUnknown() {
+	xxx_messageInfo_Message_M.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Message_M proto.InternalMessageInfo
+
+type ExtensionGroup struct {
+	ExtensionGroup       *string  `protobuf:"bytes,120,opt,name=extension_group,json=extensionGroup" json:"extension_group,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtensionGroup) Reset()         { *m = ExtensionGroup{} }
+func (m *ExtensionGroup) String() string { return proto.CompactTextString(m) }
+func (*ExtensionGroup) ProtoMessage()    {}
+func (*ExtensionGroup) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{1}
+}
+
+func (m *ExtensionGroup) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtensionGroup.Unmarshal(m, b)
+}
+func (m *ExtensionGroup) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtensionGroup.Marshal(b, m, deterministic)
+}
+func (m *ExtensionGroup) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtensionGroup.Merge(m, src)
+}
+func (m *ExtensionGroup) XXX_Size() int {
+	return xxx_messageInfo_ExtensionGroup.Size(m)
+}
+func (m *ExtensionGroup) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtensionGroup.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtensionGroup proto.InternalMessageInfo
+
+func (m *ExtensionGroup) GetExtensionGroup() string {
+	if m != nil && m.ExtensionGroup != nil {
+		return *m.ExtensionGroup
+	}
+	return ""
+}
+
+// Extend in the scope of another type.
+type ExtendingMessage struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtendingMessage) Reset()         { *m = ExtendingMessage{} }
+func (m *ExtendingMessage) String() string { return proto.CompactTextString(m) }
+func (*ExtendingMessage) ProtoMessage()    {}
+func (*ExtendingMessage) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{2}
+}
+
+func (m *ExtendingMessage) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtendingMessage.Unmarshal(m, b)
+}
+func (m *ExtendingMessage) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtendingMessage.Marshal(b, m, deterministic)
+}
+func (m *ExtendingMessage) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtendingMessage.Merge(m, src)
+}
+func (m *ExtendingMessage) XXX_Size() int {
+	return xxx_messageInfo_ExtendingMessage.Size(m)
+}
+func (m *ExtendingMessage) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtendingMessage.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtendingMessage proto.InternalMessageInfo
+
+var E_ExtendingMessage_ExtendingMessageString = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*string)(nil),
+	Field:         200,
+	Name:          "goproto.protoc.extension.ext.ExtendingMessage.extending_message_string",
+	Tag:           "bytes,200,opt,name=extending_message_string",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtendingMessage_ExtendingMessageSubmessage = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*ExtendingMessage_ExtendingMessageSubmessage)(nil),
+	Field:         201,
+	Name:          "goproto.protoc.extension.ext.ExtendingMessage.extending_message_submessage",
+	Tag:           "bytes,201,opt,name=extending_message_submessage",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+type ExtendingMessage_ExtendingMessageSubmessage struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtendingMessage_ExtendingMessageSubmessage) Reset() {
+	*m = ExtendingMessage_ExtendingMessageSubmessage{}
+}
+func (m *ExtendingMessage_ExtendingMessageSubmessage) String() string {
+	return proto.CompactTextString(m)
+}
+func (*ExtendingMessage_ExtendingMessageSubmessage) ProtoMessage() {}
+func (*ExtendingMessage_ExtendingMessageSubmessage) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{2, 0}
+}
+
+func (m *ExtendingMessage_ExtendingMessageSubmessage) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage.Unmarshal(m, b)
+}
+func (m *ExtendingMessage_ExtendingMessageSubmessage) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage.Marshal(b, m, deterministic)
+}
+func (m *ExtendingMessage_ExtendingMessageSubmessage) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage.Merge(m, src)
+}
+func (m *ExtendingMessage_ExtendingMessageSubmessage) XXX_Size() int {
+	return xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage.Size(m)
+}
+func (m *ExtendingMessage_ExtendingMessageSubmessage) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtendingMessage_ExtendingMessageSubmessage proto.InternalMessageInfo
+
+type RepeatedGroup struct {
+	RepeatedXGroup       []string `protobuf:"bytes,319,rep,name=repeated_x_group,json=repeatedXGroup" json:"repeated_x_group,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *RepeatedGroup) Reset()         { *m = RepeatedGroup{} }
+func (m *RepeatedGroup) String() string { return proto.CompactTextString(m) }
+func (*RepeatedGroup) ProtoMessage()    {}
+func (*RepeatedGroup) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{3}
+}
+
+func (m *RepeatedGroup) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_RepeatedGroup.Unmarshal(m, b)
+}
+func (m *RepeatedGroup) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_RepeatedGroup.Marshal(b, m, deterministic)
+}
+func (m *RepeatedGroup) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_RepeatedGroup.Merge(m, src)
+}
+func (m *RepeatedGroup) XXX_Size() int {
+	return xxx_messageInfo_RepeatedGroup.Size(m)
+}
+func (m *RepeatedGroup) XXX_DiscardUnknown() {
+	xxx_messageInfo_RepeatedGroup.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_RepeatedGroup proto.InternalMessageInfo
+
+func (m *RepeatedGroup) GetRepeatedXGroup() []string {
+	if m != nil {
+		return m.RepeatedXGroup
+	}
+	return nil
+}
+
+// An extension of an extension.
+type Extendable struct {
+	XXX_NoUnkeyedLiteral         struct{} `json:"-"`
+	proto.XXX_InternalExtensions `json:"-"`
+	XXX_unrecognized             []byte `json:"-"`
+	XXX_sizecache                int32  `json:"-"`
+}
+
+func (m *Extendable) Reset()         { *m = Extendable{} }
+func (m *Extendable) String() string { return proto.CompactTextString(m) }
+func (*Extendable) ProtoMessage()    {}
+func (*Extendable) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{4}
+}
+
+var extRange_Extendable = []proto.ExtensionRange{
+	{Start: 1, End: 536870911},
+}
+
+func (*Extendable) ExtensionRangeArray() []proto.ExtensionRange {
+	return extRange_Extendable
+}
+
+func (m *Extendable) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Extendable.Unmarshal(m, b)
+}
+func (m *Extendable) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Extendable.Marshal(b, m, deterministic)
+}
+func (m *Extendable) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Extendable.Merge(m, src)
+}
+func (m *Extendable) XXX_Size() int {
+	return xxx_messageInfo_Extendable.Size(m)
+}
+func (m *Extendable) XXX_DiscardUnknown() {
+	xxx_messageInfo_Extendable.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Extendable proto.InternalMessageInfo
+
+// Message set wire format.
+type MessageSetWireFormatExtension struct {
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *MessageSetWireFormatExtension) Reset()         { *m = MessageSetWireFormatExtension{} }
+func (m *MessageSetWireFormatExtension) String() string { return proto.CompactTextString(m) }
+func (*MessageSetWireFormatExtension) ProtoMessage()    {}
+func (*MessageSetWireFormatExtension) Descriptor() ([]byte, []int) {
+	return fileDescriptor_bf470ef4907b23cb, []int{5}
+}
+
+func (m *MessageSetWireFormatExtension) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_MessageSetWireFormatExtension.Unmarshal(m, b)
+}
+func (m *MessageSetWireFormatExtension) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_MessageSetWireFormatExtension.Marshal(b, m, deterministic)
+}
+func (m *MessageSetWireFormatExtension) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_MessageSetWireFormatExtension.Merge(m, src)
+}
+func (m *MessageSetWireFormatExtension) XXX_Size() int {
+	return xxx_messageInfo_MessageSetWireFormatExtension.Size(m)
+}
+func (m *MessageSetWireFormatExtension) XXX_DiscardUnknown() {
+	xxx_messageInfo_MessageSetWireFormatExtension.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_MessageSetWireFormatExtension proto.InternalMessageInfo
+
+var E_MessageSetWireFormatExtension_MessageSetField = &proto.ExtensionDesc{
+	ExtendedType:  (*base.MessageSetWireFormatMessage)(nil),
+	ExtensionType: (*MessageSetWireFormatExtension)(nil),
+	Field:         100,
+	Name:          "goproto.protoc.extension.ext.MessageSetWireFormatExtension.message_set_field",
+	Tag:           "bytes,100,opt,name=message_set_field",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionBool = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*bool)(nil),
+	Field:         101,
+	Name:          "goproto.protoc.extension.ext.extension_bool",
+	Tag:           "varint,101,opt,name=extension_bool",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionEnum = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*Enum)(nil),
+	Field:         102,
+	Name:          "goproto.protoc.extension.ext.extension_enum",
+	Tag:           "varint,102,opt,name=extension_enum,enum=goproto.protoc.extension.ext.Enum",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionInt32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int32)(nil),
+	Field:         103,
+	Name:          "goproto.protoc.extension.ext.extension_int32",
+	Tag:           "varint,103,opt,name=extension_int32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionSint32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int32)(nil),
+	Field:         104,
+	Name:          "goproto.protoc.extension.ext.extension_sint32",
+	Tag:           "zigzag32,104,opt,name=extension_sint32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionUint32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*uint32)(nil),
+	Field:         105,
+	Name:          "goproto.protoc.extension.ext.extension_uint32",
+	Tag:           "varint,105,opt,name=extension_uint32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionInt64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int64)(nil),
+	Field:         106,
+	Name:          "goproto.protoc.extension.ext.extension_int64",
+	Tag:           "varint,106,opt,name=extension_int64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionSint64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int64)(nil),
+	Field:         107,
+	Name:          "goproto.protoc.extension.ext.extension_sint64",
+	Tag:           "zigzag64,107,opt,name=extension_sint64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionUint64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*uint64)(nil),
+	Field:         108,
+	Name:          "goproto.protoc.extension.ext.extension_uint64",
+	Tag:           "varint,108,opt,name=extension_uint64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionSfixed32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int32)(nil),
+	Field:         109,
+	Name:          "goproto.protoc.extension.ext.extension_sfixed32",
+	Tag:           "fixed32,109,opt,name=extension_sfixed32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionFixed32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*uint32)(nil),
+	Field:         110,
+	Name:          "goproto.protoc.extension.ext.extension_fixed32",
+	Tag:           "fixed32,110,opt,name=extension_fixed32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionFloat = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*float32)(nil),
+	Field:         111,
+	Name:          "goproto.protoc.extension.ext.extension_float",
+	Tag:           "fixed32,111,opt,name=extension_float",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionSfixed64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*int64)(nil),
+	Field:         112,
+	Name:          "goproto.protoc.extension.ext.extension_sfixed64",
+	Tag:           "fixed64,112,opt,name=extension_sfixed64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionFixed64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*uint64)(nil),
+	Field:         113,
+	Name:          "goproto.protoc.extension.ext.extension_fixed64",
+	Tag:           "fixed64,113,opt,name=extension_fixed64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionDouble = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*float64)(nil),
+	Field:         114,
+	Name:          "goproto.protoc.extension.ext.extension_double",
+	Tag:           "fixed64,114,opt,name=extension_double",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionString = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*string)(nil),
+	Field:         115,
+	Name:          "goproto.protoc.extension.ext.extension_string",
+	Tag:           "bytes,115,opt,name=extension_string",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtensionBytes = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]byte)(nil),
+	Field:         116,
+	Name:          "goproto.protoc.extension.ext.extension_bytes",
+	Tag:           "bytes,116,opt,name=extension_bytes",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_Extension_Message = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*Message)(nil),
+	Field:         117,
+	Name:          "goproto.protoc.extension.ext.extension_Message",
+	Tag:           "bytes,117,opt,name=extension_Message",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_Extension_MessageM = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*Message_M)(nil),
+	Field:         118,
+	Name:          "goproto.protoc.extension.ext.extension_MessageM",
+	Tag:           "bytes,118,opt,name=extension_MessageM",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_Extensiongroup = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*ExtensionGroup)(nil),
+	Field:         119,
+	Name:          "goproto.protoc.extension.ext.extensiongroup",
+	Tag:           "group,119,opt,name=ExtensionGroup",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtraMessage = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*extra.ExtraMessage)(nil),
+	Field:         9,
+	Name:          "goproto.protoc.extension.ext.extra_message",
+	Tag:           "bytes,9,opt,name=extra_message",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXBool = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]bool)(nil),
+	Field:         301,
+	Name:          "goproto.protoc.extension.ext.repeated_x_bool",
+	Tag:           "varint,301,rep,name=repeated_x_bool",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXEnum = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]Enum)(nil),
+	Field:         302,
+	Name:          "goproto.protoc.extension.ext.repeated_x_enum",
+	Tag:           "varint,302,rep,name=repeated_x_enum,enum=goproto.protoc.extension.ext.Enum",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXInt32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int32)(nil),
+	Field:         303,
+	Name:          "goproto.protoc.extension.ext.repeated_x_int32",
+	Tag:           "varint,303,rep,name=repeated_x_int32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXSint32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int32)(nil),
+	Field:         304,
+	Name:          "goproto.protoc.extension.ext.repeated_x_sint32",
+	Tag:           "zigzag32,304,rep,name=repeated_x_sint32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXUint32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]uint32)(nil),
+	Field:         305,
+	Name:          "goproto.protoc.extension.ext.repeated_x_uint32",
+	Tag:           "varint,305,rep,name=repeated_x_uint32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXInt64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int64)(nil),
+	Field:         306,
+	Name:          "goproto.protoc.extension.ext.repeated_x_int64",
+	Tag:           "varint,306,rep,name=repeated_x_int64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXSint64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int64)(nil),
+	Field:         307,
+	Name:          "goproto.protoc.extension.ext.repeated_x_sint64",
+	Tag:           "zigzag64,307,rep,name=repeated_x_sint64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXUint64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]uint64)(nil),
+	Field:         308,
+	Name:          "goproto.protoc.extension.ext.repeated_x_uint64",
+	Tag:           "varint,308,rep,name=repeated_x_uint64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXSfixed32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int32)(nil),
+	Field:         309,
+	Name:          "goproto.protoc.extension.ext.repeated_x_sfixed32",
+	Tag:           "fixed32,309,rep,name=repeated_x_sfixed32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXFixed32 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]uint32)(nil),
+	Field:         310,
+	Name:          "goproto.protoc.extension.ext.repeated_x_fixed32",
+	Tag:           "fixed32,310,rep,name=repeated_x_fixed32",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXFloat = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]float32)(nil),
+	Field:         311,
+	Name:          "goproto.protoc.extension.ext.repeated_x_float",
+	Tag:           "fixed32,311,rep,name=repeated_x_float",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXSfixed64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]int64)(nil),
+	Field:         312,
+	Name:          "goproto.protoc.extension.ext.repeated_x_sfixed64",
+	Tag:           "fixed64,312,rep,name=repeated_x_sfixed64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXFixed64 = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]uint64)(nil),
+	Field:         313,
+	Name:          "goproto.protoc.extension.ext.repeated_x_fixed64",
+	Tag:           "fixed64,313,rep,name=repeated_x_fixed64",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXDouble = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]float64)(nil),
+	Field:         314,
+	Name:          "goproto.protoc.extension.ext.repeated_x_double",
+	Tag:           "fixed64,314,rep,name=repeated_x_double",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXString = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]string)(nil),
+	Field:         315,
+	Name:          "goproto.protoc.extension.ext.repeated_x_string",
+	Tag:           "bytes,315,rep,name=repeated_x_string",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedXBytes = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([][]byte)(nil),
+	Field:         316,
+	Name:          "goproto.protoc.extension.ext.repeated_x_bytes",
+	Tag:           "bytes,316,rep,name=repeated_x_bytes",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_RepeatedX_Message = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]*Message)(nil),
+	Field:         317,
+	Name:          "goproto.protoc.extension.ext.repeated_x_Message",
+	Tag:           "bytes,317,rep,name=repeated_x_Message",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_Repeatedgroup = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: ([]*RepeatedGroup)(nil),
+	Field:         318,
+	Name:          "goproto.protoc.extension.ext.repeatedgroup",
+	Tag:           "group,318,rep,name=RepeatedGroup",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtendableField = &proto.ExtensionDesc{
+	ExtendedType:  (*base.BaseMessage)(nil),
+	ExtensionType: (*Extendable)(nil),
+	Field:         400,
+	Name:          "goproto.protoc.extension.ext.extendable_field",
+	Tag:           "bytes,400,opt,name=extendable_field",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+var E_ExtendableStringField = &proto.ExtensionDesc{
+	ExtendedType:  (*Extendable)(nil),
+	ExtensionType: (*string)(nil),
+	Field:         1,
+	Name:          "goproto.protoc.extension.ext.extendable_string_field",
+	Tag:           "bytes,1,opt,name=extendable_string_field",
+	Filename:      "extensions/ext/ext.proto",
+}
+
+func init() {
+	proto.RegisterType((*Message)(nil), "goproto.protoc.extension.ext.Message")
+	proto.RegisterType((*Message_M)(nil), "goproto.protoc.extension.ext.Message.M")
+	proto.RegisterType((*ExtensionGroup)(nil), "goproto.protoc.extension.ext.ExtensionGroup")
+	proto.RegisterType((*ExtendingMessage)(nil), "goproto.protoc.extension.ext.ExtendingMessage")
+	proto.RegisterType((*ExtendingMessage_ExtendingMessageSubmessage)(nil), "goproto.protoc.extension.ext.ExtendingMessage.ExtendingMessageSubmessage")
+	proto.RegisterType((*RepeatedGroup)(nil), "goproto.protoc.extension.ext.RepeatedGroup")
+	proto.RegisterType((*Extendable)(nil), "goproto.protoc.extension.ext.Extendable")
+	proto.RegisterType((*MessageSetWireFormatExtension)(nil), "goproto.protoc.extension.ext.MessageSetWireFormatExtension")
+	proto.RegisterEnum("goproto.protoc.extension.ext.Enum", Enum_name, Enum_value)
+	proto.RegisterExtension(E_ExtendingMessage_ExtendingMessageString)
+	proto.RegisterExtension(E_ExtendingMessage_ExtendingMessageSubmessage)
+	proto.RegisterExtension(E_MessageSetWireFormatExtension_MessageSetField)
+	proto.RegisterExtension(E_ExtensionBool)
+	proto.RegisterExtension(E_ExtensionEnum)
+	proto.RegisterExtension(E_ExtensionInt32)
+	proto.RegisterExtension(E_ExtensionSint32)
+	proto.RegisterExtension(E_ExtensionUint32)
+	proto.RegisterExtension(E_ExtensionInt64)
+	proto.RegisterExtension(E_ExtensionSint64)
+	proto.RegisterExtension(E_ExtensionUint64)
+	proto.RegisterExtension(E_ExtensionSfixed32)
+	proto.RegisterExtension(E_ExtensionFixed32)
+	proto.RegisterExtension(E_ExtensionFloat)
+	proto.RegisterExtension(E_ExtensionSfixed64)
+	proto.RegisterExtension(E_ExtensionFixed64)
+	proto.RegisterExtension(E_ExtensionDouble)
+	proto.RegisterExtension(E_ExtensionString)
+	proto.RegisterExtension(E_ExtensionBytes)
+	proto.RegisterExtension(E_Extension_Message)
+	proto.RegisterExtension(E_Extension_MessageM)
+	proto.RegisterExtension(E_Extensiongroup)
+	proto.RegisterExtension(E_ExtraMessage)
+	proto.RegisterExtension(E_RepeatedXBool)
+	proto.RegisterExtension(E_RepeatedXEnum)
+	proto.RegisterExtension(E_RepeatedXInt32)
+	proto.RegisterExtension(E_RepeatedXSint32)
+	proto.RegisterExtension(E_RepeatedXUint32)
+	proto.RegisterExtension(E_RepeatedXInt64)
+	proto.RegisterExtension(E_RepeatedXSint64)
+	proto.RegisterExtension(E_RepeatedXUint64)
+	proto.RegisterExtension(E_RepeatedXSfixed32)
+	proto.RegisterExtension(E_RepeatedXFixed32)
+	proto.RegisterExtension(E_RepeatedXFloat)
+	proto.RegisterExtension(E_RepeatedXSfixed64)
+	proto.RegisterExtension(E_RepeatedXFixed64)
+	proto.RegisterExtension(E_RepeatedXDouble)
+	proto.RegisterExtension(E_RepeatedXString)
+	proto.RegisterExtension(E_RepeatedXBytes)
+	proto.RegisterExtension(E_RepeatedX_Message)
+	proto.RegisterExtension(E_Repeatedgroup)
+	proto.RegisterExtension(E_ExtendableField)
+	proto.RegisterExtension(E_ExtendableStringField)
+}
+
+func init() { proto.RegisterFile("extensions/ext/ext.proto", fileDescriptor_bf470ef4907b23cb) }
+
+var fileDescriptor_bf470ef4907b23cb = []byte{
+	// 1105 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x9c, 0x98, 0x5b, 0x6f, 0xe3, 0x44,
+	0x14, 0xc7, 0x99, 0x24, 0xbb, 0xcd, 0x0e, 0x4d, 0x9b, 0x18, 0xb1, 0x44, 0x51, 0x91, 0x46, 0x91,
+	0xd0, 0x0e, 0x85, 0x75, 0xa5, 0x10, 0x45, 0xc2, 0x3c, 0x51, 0x68, 0xd1, 0x3e, 0x44, 0x08, 0x57,
+	0x55, 0xbb, 0xcb, 0x43, 0x70, 0xea, 0xa9, 0x31, 0x38, 0x9e, 0xe2, 0x0b, 0x1b, 0x1e, 0x58, 0x45,
+	0x7c, 0x02, 0xbe, 0x03, 0xcf, 0xdc, 0x6f, 0xcb, 0xfd, 0x09, 0x09, 0x5e, 0xf9, 0x44, 0x68, 0x66,
+	0x7c, 0x19, 0x3b, 0x69, 0x36, 0xe3, 0x87, 0x56, 0x93, 0xb1, 0xf3, 0x3b, 0xc7, 0xff, 0x73, 0xe2,
+	0xff, 0xb1, 0x61, 0x97, 0xcc, 0x23, 0xe2, 0x87, 0x2e, 0xf5, 0xc3, 0x03, 0x32, 0x8f, 0xd8, 0x9f,
+	0x7e, 0x15, 0xd0, 0x88, 0x6a, 0x7b, 0x0e, 0xe5, 0x0b, 0xf1, 0xf1, 0x42, 0xcf, 0x4e, 0x64, 0xab,
+	0x5e, 0x4f, 0xfa, 0xde, 0xd4, 0x0a, 0x09, 0xff, 0x27, 0x4e, 0xed, 0xed, 0x15, 0x99, 0x81, 0x25,
+	0xfe, 0x8b, 0xa3, 0xfd, 0x3e, 0xdc, 0x1a, 0x93, 0x30, 0xb4, 0x1c, 0xa2, 0x69, 0xb0, 0x61, 0x5b,
+	0x91, 0xd5, 0x05, 0x08, 0xe0, 0x6d, 0x93, 0xaf, 0x7b, 0x75, 0x08, 0xc6, 0xfd, 0x57, 0xe1, 0xce,
+	0x51, 0xca, 0x78, 0x2b, 0xa0, 0xf1, 0x95, 0x76, 0x07, 0xee, 0x66, 0xd4, 0x89, 0xc3, 0xb6, 0xba,
+	0x73, 0x04, 0xf0, 0x2d, 0x73, 0x87, 0x14, 0x4e, 0xec, 0xff, 0x57, 0x83, 0x6d, 0xfe, 0x5d, 0xdb,
+	0xf5, 0x9d, 0x24, 0x50, 0x6f, 0x0f, 0xf6, 0xca, 0x7b, 0x27, 0xf1, 0x74, 0x26, 0x56, 0x03, 0x92,
+	0xa8, 0xc0, 0x8e, 0x4e, 0x92, 0xcd, 0x49, 0x18, 0x05, 0xae, 0xef, 0x68, 0xfb, 0xfa, 0xb5, 0x32,
+	0xf0, 0x2b, 0x3e, 0xb4, 0x42, 0x92, 0x10, 0xbb, 0xff, 0x00, 0x9e, 0xd1, 0x6d, 0x52, 0x0e, 0xc5,
+	0x51, 0x83, 0xc7, 0x00, 0xee, 0xad, 0x88, 0x93, 0xe5, 0xa1, 0x14, 0xeb, 0x5f, 0x16, 0xeb, 0xe9,
+	0xc1, 0x3d, 0x7d, 0x5d, 0x95, 0xf4, 0xf2, 0x45, 0xeb, 0xd7, 0xab, 0x60, 0xf6, 0xc8, 0xb5, 0xc7,
+	0xfa, 0x06, 0x6c, 0x99, 0xe4, 0x8a, 0x58, 0x11, 0xb1, 0x45, 0x39, 0x5e, 0x84, 0xed, 0x20, 0xd9,
+	0x98, 0xcc, 0x93, 0x7a, 0xfc, 0x55, 0x43, 0x75, 0x56, 0x90, 0xf4, 0xc0, 0xb9, 0x28, 0xc8, 0x6d,
+	0x08, 0x45, 0x54, 0x6b, 0xea, 0x91, 0xfd, 0x66, 0x13, 0xb4, 0x17, 0x8b, 0xc5, 0xa2, 0xd6, 0xff,
+	0x1b, 0xc0, 0xe7, 0xd3, 0x48, 0x24, 0x3a, 0x73, 0x03, 0x72, 0x4c, 0x83, 0x99, 0x15, 0x65, 0x85,
+	0x1f, 0x7c, 0x01, 0x60, 0x27, 0x93, 0x89, 0x44, 0x93, 0x4b, 0x97, 0x78, 0xb6, 0x66, 0x3c, 0x41,
+	0xa5, 0x55, 0xcc, 0x54, 0x35, 0x9b, 0x8b, 0xf6, 0xda, 0x7a, 0xd1, 0xd6, 0x26, 0x65, 0xee, 0xce,
+	0xb2, 0xc3, 0xc7, 0x2c, 0x9f, 0xfd, 0x36, 0x6c, 0x1c, 0xf9, 0xf1, 0x4c, 0x6b, 0xc2, 0xc6, 0x83,
+	0x23, 0xf3, 0xed, 0xf6, 0x53, 0xc6, 0x3b, 0x30, 0x6f, 0xca, 0xc9, 0x94, 0x52, 0x4f, 0xa9, 0xb2,
+	0x04, 0x01, 0xdc, 0x34, 0x5b, 0xd9, 0x19, 0x87, 0x94, 0x7a, 0x46, 0x2c, 0x23, 0x09, 0x0b, 0xa7,
+	0x82, 0xbc, 0x44, 0x00, 0xef, 0x0c, 0xfa, 0x4f, 0xe8, 0x15, 0x3f, 0x9e, 0x49, 0x61, 0xd9, 0x47,
+	0xe3, 0x44, 0xfe, 0xd5, 0xb9, 0x7e, 0xf4, 0xca, 0x40, 0x29, 0xae, 0x83, 0x00, 0xbe, 0x21, 0xfd,
+	0x42, 0xef, 0x31, 0x82, 0x71, 0x0a, 0xdb, 0x39, 0x34, 0x54, 0xa7, 0xbe, 0x8f, 0x00, 0xee, 0x98,
+	0x79, 0x62, 0x27, 0xee, 0x32, 0x36, 0x56, 0xc7, 0xba, 0x08, 0xe0, 0x96, 0x84, 0x3d, 0x15, 0xd8,
+	0xb2, 0x04, 0xa3, 0xa1, 0x12, 0xf5, 0x03, 0x04, 0x70, 0xbd, 0x28, 0xc1, 0x68, 0xb8, 0x2c, 0x81,
+	0x22, 0xf5, 0x43, 0x04, 0xb0, 0x56, 0x92, 0xa0, 0x8c, 0x8d, 0xd5, 0xb1, 0x1e, 0x02, 0xb8, 0x51,
+	0x92, 0x60, 0x34, 0x34, 0xee, 0x43, 0x4d, 0xca, 0xf6, 0xd2, 0x9d, 0x13, 0x5b, 0x51, 0xdb, 0x19,
+	0x02, 0x78, 0xd7, 0xec, 0xe4, 0xf9, 0x26, 0x10, 0xe3, 0x0c, 0xe6, 0x9b, 0x93, 0x2a, 0x64, 0x1f,
+	0x01, 0xbc, 0x65, 0xe6, 0x97, 0x7d, 0x9c, 0x80, 0x0b, 0x65, 0xbb, 0xf4, 0xa8, 0x15, 0x29, 0x61,
+	0x29, 0x02, 0xb8, 0x26, 0x95, 0xed, 0x98, 0x11, 0x56, 0x09, 0xa1, 0xa8, 0xf0, 0x15, 0x02, 0xb8,
+	0xbd, 0x24, 0xc4, 0x68, 0xb8, 0x42, 0x08, 0x45, 0xf2, 0x47, 0x08, 0xe0, 0x9b, 0x65, 0x21, 0xca,
+	0x3d, 0x61, 0xd3, 0x78, 0xea, 0xa9, 0x19, 0x4d, 0x80, 0x00, 0x06, 0x52, 0x4f, 0xbc, 0xc9, 0x11,
+	0xa5, 0x0e, 0x56, 0xf7, 0xca, 0x90, 0x5b, 0xa5, 0xd4, 0xc1, 0x1c, 0x51, 0x2c, 0xdb, 0xf4, 0x93,
+	0x88, 0x84, 0x4a, 0xd4, 0x88, 0x0f, 0x12, 0x79, 0xd9, 0x0e, 0x19, 0xc1, 0x78, 0x24, 0x6b, 0x3b,
+	0xae, 0x60, 0xb6, 0x31, 0xb7, 0x8d, 0x17, 0x36, 0xb2, 0x0d, 0xa9, 0x04, 0xc9, 0x8e, 0xf1, 0x19,
+	0x90, 0xfb, 0x26, 0xd9, 0x1d, 0x2b, 0x65, 0xf0, 0x31, 0xcf, 0xe0, 0xce, 0x46, 0x19, 0xe8, 0x63,
+	0xa9, 0xc1, 0xd2, 0x68, 0xc6, 0x02, 0x48, 0x16, 0xc2, 0x0d, 0x5b, 0x29, 0x81, 0x87, 0x08, 0x60,
+	0x38, 0x78, 0x79, 0x83, 0x71, 0x23, 0x1b, 0xc5, 0xcc, 0x52, 0x3c, 0xe3, 0x53, 0xd8, 0xe2, 0x83,
+	0xe0, 0xa4, 0xca, 0xc0, 0x73, 0x8b, 0x2b, 0xb0, 0x3e, 0x81, 0xc0, 0x62, 0x29, 0x04, 0x56, 0x5a,
+	0x8a, 0x6d, 0x22, 0x7d, 0x62, 0xbd, 0x25, 0xcd, 0x2c, 0xca, 0xbe, 0xfc, 0x25, 0x1b, 0x6f, 0x9a,
+	0x66, 0x2b, 0x1b, 0x6f, 0xb8, 0x31, 0x3f, 0x2c, 0x40, 0x95, 0x9d, 0xf9, 0x2b, 0x06, 0xdd, 0xd0,
+	0x9a, 0xb3, 0xc0, 0xdc, 0x9a, 0x4f, 0x0b, 0x13, 0x98, 0xba, 0xdd, 0x7d, 0xcd, 0x22, 0xdf, 0x90,
+	0xa6, 0x35, 0x61, 0xce, 0x67, 0xb0, 0x23, 0x61, 0x2b, 0xb8, 0xf3, 0x37, 0x8c, 0xdb, 0x31, 0x33,
+	0x55, 0xce, 0x13, 0x7b, 0x2e, 0x82, 0x2b, 0xf8, 0xf3, 0xb7, 0x0c, 0xdc, 0x92, 0xc0, 0xa7, 0x99,
+	0xef, 0x17, 0x85, 0x50, 0xbc, 0x71, 0x7e, 0xc7, 0xb8, 0xf5, 0xa2, 0x10, 0xe2, 0x86, 0x5c, 0x12,
+	0x42, 0x91, 0xfb, 0x3d, 0xe3, 0x6a, 0x25, 0x21, 0x96, 0xc0, 0x15, 0x5c, 0xfa, 0x07, 0x06, 0x6e,
+	0x94, 0x84, 0x18, 0x0d, 0x8d, 0x77, 0xe1, 0x33, 0x72, 0xc6, 0x55, 0xdc, 0xf4, 0x47, 0x86, 0xde,
+	0x35, 0x3b, 0x79, 0xce, 0xa9, 0x51, 0xdf, 0x87, 0x9a, 0x04, 0xaf, 0xc2, 0xfe, 0x89, 0xb1, 0xb7,
+	0xcc, 0xac, 0x58, 0xe7, 0xa9, 0x55, 0x17, 0x0b, 0xa8, 0xee, 0xd5, 0x3f, 0x33, 0x70, 0x4d, 0x2a,
+	0xa0, 0x30, 0xeb, 0x55, 0x72, 0x28, 0x2a, 0xfd, 0x98, 0x91, 0xdb, 0x4b, 0x72, 0x88, 0x91, 0xa8,
+	0x2c, 0x87, 0x22, 0xfb, 0x17, 0xc6, 0xbe, 0x59, 0x96, 0x63, 0xa9, 0x3f, 0x2a, 0x38, 0xf6, 0xaf,
+	0x8c, 0x0c, 0xa4, 0xfe, 0x48, 0x2c, 0xbb, 0xd4, 0xd1, 0xea, 0x9e, 0xfd, 0x9b, 0x78, 0xc0, 0x93,
+	0x3a, 0x5a, 0x98, 0x76, 0xb1, 0x80, 0xea, 0xae, 0xfd, 0x3b, 0xe3, 0x6e, 0x4b, 0x05, 0x14, 0xb6,
+	0xbd, 0x00, 0x05, 0x91, 0xab, 0x18, 0xf7, 0x1f, 0x8c, 0xbc, 0xb9, 0x73, 0x67, 0x09, 0xa4, 0x96,
+	0xf1, 0x08, 0x66, 0x77, 0x5d, 0x75, 0xcb, 0xfc, 0x93, 0x05, 0x87, 0x83, 0x97, 0xd6, 0x07, 0x2f,
+	0x3c, 0x57, 0x9b, 0xc5, 0x70, 0x4c, 0x02, 0x31, 0x4e, 0xf0, 0x87, 0xe7, 0xe4, 0x01, 0x58, 0x25,
+	0x87, 0xcf, 0xeb, 0xdc, 0x36, 0xf1, 0x26, 0xaf, 0x09, 0x58, 0x88, 0x64, 0x22, 0xe3, 0x6b, 0xfe,
+	0x78, 0x6b, 0xbc, 0x07, 0x9f, 0x93, 0x32, 0x10, 0x5d, 0x93, 0x24, 0xb2, 0x31, 0xb5, 0x2b, 0x5e,
+	0x8c, 0x3c, 0x9b, 0x83, 0x44, 0xe7, 0xf0, 0x08, 0x87, 0x6f, 0x3c, 0x78, 0xdd, 0xa1, 0xd4, 0xf1,
+	0x88, 0xee, 0x50, 0xcf, 0xf2, 0x1d, 0x9d, 0x06, 0xce, 0x01, 0x27, 0x1e, 0x5c, 0xcc, 0x6c, 0xb1,
+	0xba, 0xb8, 0xeb, 0x10, 0xff, 0xae, 0x43, 0x0f, 0x22, 0x12, 0x46, 0xb6, 0x15, 0xf1, 0x57, 0x4a,
+	0xd2, 0x3b, 0xa6, 0xff, 0x03, 0x00, 0x00, 0xff, 0xff, 0xa5, 0xa0, 0x8e, 0xb5, 0xc8, 0x12, 0x00,
+	0x00,
+}
diff --git a/cmd/protoc-gen-go/testdata/extensions/ext/ext.proto b/cmd/protoc-gen-go/testdata/extensions/ext/ext.proto
new file mode 100644
index 0000000..3767b1e
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/ext/ext.proto
@@ -0,0 +1,103 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+syntax = "proto2";
+
+import "extensions/base/base.proto";
+import "extensions/extra/extra.proto";
+
+package goproto.protoc.extension.ext;
+
+option go_package = "google.golang.org/proto/cmd/protoc-gen-go/testdata/extensions/ext";
+
+message Message {
+  optional bytes data = 1;
+
+  message M {}
+}
+
+enum Enum {
+  ZERO = 0;
+}
+
+// Extend with various types.
+extend goproto.protoc.extension.base.BaseMessage {
+  optional bool      extension_bool     = 101;
+  optional Enum      extension_enum     = 102;
+  optional int32     extension_int32    = 103;
+  optional sint32    extension_sint32   = 104;
+  optional uint32    extension_uint32   = 105;
+  optional int64     extension_int64    = 106;
+  optional sint64    extension_sint64   = 107;
+  optional uint64    extension_uint64   = 108;
+  optional sfixed32  extension_sfixed32 = 109;
+  optional fixed32   extension_fixed32  = 110;
+  optional float     extension_float    = 111;
+  optional sfixed64  extension_sfixed64 = 112;
+  optional fixed64   extension_fixed64  = 113;
+  optional double    extension_double   = 114;
+  optional string    extension_string   = 115;
+  optional bytes     extension_bytes    = 116;
+  optional Message   extension_Message  = 117;
+  optional Message.M extension_MessageM = 118;
+  optional group ExtensionGroup = 119 {
+    optional string extension_group = 120;
+  }
+}
+
+// Extend with a foreign message.
+extend goproto.protoc.extension.base.BaseMessage {
+  optional goproto.protoc.extension.extra.ExtraMessage extra_message = 9;
+}
+
+// Extend in the scope of another type.
+message ExtendingMessage {
+  extend goproto.protoc.extension.base.BaseMessage {
+    optional string extending_message_string = 200;
+    optional ExtendingMessageSubmessage extending_message_submessage = 201;
+  }
+  message ExtendingMessageSubmessage {}
+}
+
+// Extend with repeated fields.
+extend goproto.protoc.extension.base.BaseMessage {
+  repeated bool     repeated_x_bool     = 301;
+  repeated Enum     repeated_x_enum     = 302;
+  repeated int32    repeated_x_int32    = 303;
+  repeated sint32   repeated_x_sint32   = 304;
+  repeated uint32   repeated_x_uint32   = 305;
+  repeated int64    repeated_x_int64    = 306;
+  repeated sint64   repeated_x_sint64   = 307;
+  repeated uint64   repeated_x_uint64   = 308;
+  repeated sfixed32 repeated_x_sfixed32 = 309;
+  repeated fixed32  repeated_x_fixed32  = 310;
+  repeated float    repeated_x_float    = 311;
+  repeated sfixed64 repeated_x_sfixed64 = 312;
+  repeated fixed64  repeated_x_fixed64  = 313;
+  repeated double   repeated_x_double   = 314;
+  repeated string   repeated_x_string   = 315;
+  repeated bytes    repeated_x_bytes    = 316;
+  repeated Message  repeated_x_Message  = 317;
+  repeated group RepeatedGroup = 318 {
+    repeated string repeated_x_group = 319;
+  }
+}
+
+// An extension of an extension.
+message Extendable {
+  extensions 1 to max;
+}
+extend goproto.protoc.extension.base.BaseMessage {
+  optional Extendable extendable_field = 400;
+}
+extend Extendable {
+  optional string extendable_string_field = 1;
+}
+
+// Message set wire format.
+message MessageSetWireFormatExtension {
+  extend goproto.protoc.extension.base.MessageSetWireFormatMessage {
+    optional MessageSetWireFormatExtension message_set_field = 100;
+  }
+}
diff --git a/cmd/protoc-gen-go/testdata/extensions/extra/extra.pb.go b/cmd/protoc-gen-go/testdata/extensions/extra/extra.pb.go
new file mode 100644
index 0000000..baf4a3d
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/extra/extra.pb.go
@@ -0,0 +1,79 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: extensions/extra/extra.proto
+
+package extra
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type ExtraMessage struct {
+	Data                 []byte   `protobuf:"bytes,1,opt,name=data" json:"data,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtraMessage) Reset()         { *m = ExtraMessage{} }
+func (m *ExtraMessage) String() string { return proto.CompactTextString(m) }
+func (*ExtraMessage) ProtoMessage()    {}
+func (*ExtraMessage) Descriptor() ([]byte, []int) {
+	return fileDescriptor_496c2a5e9c1e8739, []int{0}
+}
+
+func (m *ExtraMessage) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtraMessage.Unmarshal(m, b)
+}
+func (m *ExtraMessage) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtraMessage.Marshal(b, m, deterministic)
+}
+func (m *ExtraMessage) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtraMessage.Merge(m, src)
+}
+func (m *ExtraMessage) XXX_Size() int {
+	return xxx_messageInfo_ExtraMessage.Size(m)
+}
+func (m *ExtraMessage) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtraMessage.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtraMessage proto.InternalMessageInfo
+
+func (m *ExtraMessage) GetData() []byte {
+	if m != nil {
+		return m.Data
+	}
+	return nil
+}
+
+func init() {
+	proto.RegisterType((*ExtraMessage)(nil), "goproto.protoc.extension.extra.ExtraMessage")
+}
+
+func init() { proto.RegisterFile("extensions/extra/extra.proto", fileDescriptor_496c2a5e9c1e8739) }
+
+var fileDescriptor_496c2a5e9c1e8739 = []byte{
+	// 143 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x92, 0x49, 0xad, 0x28, 0x49,
+	0xcd, 0x2b, 0xce, 0xcc, 0xcf, 0x2b, 0xd6, 0x4f, 0xad, 0x28, 0x29, 0x4a, 0x84, 0x90, 0x7a, 0x05,
+	0x45, 0xf9, 0x25, 0xf9, 0x42, 0x72, 0xe9, 0xf9, 0x60, 0x06, 0x84, 0x9b, 0xac, 0x07, 0x57, 0xac,
+	0x07, 0x56, 0xa5, 0xa4, 0xc4, 0xc5, 0xe3, 0x0a, 0x62, 0xf8, 0xa6, 0x16, 0x17, 0x27, 0xa6, 0xa7,
+	0x0a, 0x09, 0x71, 0xb1, 0xa4, 0x24, 0x96, 0x24, 0x4a, 0x30, 0x2a, 0x30, 0x6a, 0xf0, 0x04, 0x81,
+	0xd9, 0x4e, 0xae, 0x51, 0xce, 0xe9, 0xf9, 0xf9, 0xe9, 0x39, 0xa9, 0x7a, 0xe9, 0xf9, 0x39, 0x89,
+	0x79, 0xe9, 0x7a, 0xf9, 0x45, 0xe9, 0xfa, 0x60, 0xf3, 0xf4, 0x93, 0x73, 0x53, 0x20, 0xac, 0x64,
+	0xdd, 0xf4, 0xd4, 0x3c, 0xdd, 0xf4, 0x7c, 0xfd, 0x92, 0xd4, 0xe2, 0x12, 0x90, 0x2e, 0x7d, 0x74,
+	0x67, 0x01, 0x02, 0x00, 0x00, 0xff, 0xff, 0xa9, 0xe3, 0x2f, 0xd9, 0xa9, 0x00, 0x00, 0x00,
+}
diff --git a/cmd/protoc-gen-go/testdata/extensions/extra/extra.proto b/cmd/protoc-gen-go/testdata/extensions/extra/extra.proto
new file mode 100644
index 0000000..84a4392
--- /dev/null
+++ b/cmd/protoc-gen-go/testdata/extensions/extra/extra.proto
@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+syntax = "proto2";
+
+package goproto.protoc.extension.extra;
+
+option go_package = "google.golang.org/proto/cmd/protoc-gen-go/testdata/extensions/extra";
+
+message ExtraMessage {
+  optional bytes data = 1;
+}
diff --git a/cmd/protoc-gen-go/testdata/fieldnames/fieldnames.pb.go b/cmd/protoc-gen-go/testdata/fieldnames/fieldnames.pb.go
index ee87a4f..570e348 100644
--- a/cmd/protoc-gen-go/testdata/fieldnames/fieldnames.pb.go
+++ b/cmd/protoc-gen-go/testdata/fieldnames/fieldnames.pb.go
@@ -66,6 +66,7 @@
 func (*Message) Descriptor() ([]byte, []int) {
 	return fileDescriptor_6bbe3f70febb9403, []int{0}
 }
+
 func (m *Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/fmt/m.pb.go b/cmd/protoc-gen-go/testdata/imports/fmt/m.pb.go
index e58ba47..ec263db 100644
--- a/cmd/protoc-gen-go/testdata/imports/fmt/m.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/fmt/m.pb.go
@@ -32,6 +32,7 @@
 func (*M) Descriptor() ([]byte, []int) {
 	return fileDescriptor_72c126fcd452e392, []int{0}
 }
+
 func (m *M) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go b/cmd/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
index 36012e1..9043697 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
@@ -54,6 +54,7 @@
 func (*M1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_c1091de3fa870a14, []int{0}
 }
+
 func (m *M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M1.Unmarshal(m, b)
 }
@@ -85,6 +86,7 @@
 func (*M1_1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_c1091de3fa870a14, []int{1}
 }
+
 func (m *M1_1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M1_1.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go b/cmd/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
index a87cecc..9b6cd05 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
@@ -32,6 +32,7 @@
 func (*M2) Descriptor() ([]byte, []int) {
 	return fileDescriptor_20cf27515c0d621c, []int{0}
 }
+
 func (m *M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M2.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go b/cmd/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
index 437e3f8..61b5155 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
@@ -32,6 +32,7 @@
 func (*M3) Descriptor() ([]byte, []int) {
 	return fileDescriptor_ff9d8f834875c9c5, []int{0}
 }
+
 func (m *M3) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M3.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go b/cmd/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
index 9f35f3f..19b0bd8 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
@@ -32,6 +32,7 @@
 func (*M4) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fdd24f82f6c5a786, []int{0}
 }
+
 func (m *M4) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M4.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go b/cmd/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
index a54118d..d15f4c9 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
@@ -32,6 +32,7 @@
 func (*M1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_7f49573d035512a8, []int{0}
 }
+
 func (m *M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M1.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go b/cmd/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
index 2b86237..66e66de 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
@@ -32,6 +32,7 @@
 func (*M2) Descriptor() ([]byte, []int) {
 	return fileDescriptor_a1becddceeb586f2, []int{0}
 }
+
 func (m *M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M2.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go b/cmd/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
index 58e1437..6713a20 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
@@ -34,6 +34,7 @@
 func (*A1M1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_3b904a47327455f3, []int{0}
 }
+
 func (m *A1M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_A1M1.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go b/cmd/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
index 0586065..a0a1588 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
@@ -34,6 +34,7 @@
 func (*A1M2) Descriptor() ([]byte, []int) {
 	return fileDescriptor_bdb27b114687957d, []int{0}
 }
+
 func (m *A1M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_A1M2.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/imports/test_import_all.pb.go b/cmd/protoc-gen-go/testdata/imports/test_import_all.pb.go
index 6722483..1746f9d 100644
--- a/cmd/protoc-gen-go/testdata/imports/test_import_all.pb.go
+++ b/cmd/protoc-gen-go/testdata/imports/test_import_all.pb.go
@@ -43,6 +43,7 @@
 func (*All) Descriptor() ([]byte, []int) {
 	return fileDescriptor_324466f0afc16f77, []int{0}
 }
+
 func (m *All) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_All.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/proto2/enum.pb.go b/cmd/protoc-gen-go/testdata/proto2/enum.pb.go
index 7842bc7..b592bd0 100644
--- a/cmd/protoc-gen-go/testdata/proto2/enum.pb.go
+++ b/cmd/protoc-gen-go/testdata/proto2/enum.pb.go
@@ -267,6 +267,7 @@
 func (*EnumContainerMessage1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_de9f68860d540858, []int{0}
 }
+
 func (m *EnumContainerMessage1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_EnumContainerMessage1.Unmarshal(m, b)
 }
@@ -301,6 +302,7 @@
 func (*EnumContainerMessage1_EnumContainerMessage2) Descriptor() ([]byte, []int) {
 	return fileDescriptor_de9f68860d540858, []int{0, 0}
 }
+
 func (m *EnumContainerMessage1_EnumContainerMessage2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_EnumContainerMessage1_EnumContainerMessage2.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/proto2/fields.pb.go b/cmd/protoc-gen-go/testdata/proto2/fields.pb.go
index 9f6421d..bba5924 100644
--- a/cmd/protoc-gen-go/testdata/proto2/fields.pb.go
+++ b/cmd/protoc-gen-go/testdata/proto2/fields.pb.go
@@ -175,6 +175,7 @@
 func (*FieldTestMessage) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0}
 }
+
 func (m *FieldTestMessage) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage.Unmarshal(m, b)
 }
@@ -1409,6 +1410,7 @@
 func (*FieldTestMessage_OptionalGroup) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0, 0}
 }
+
 func (m *FieldTestMessage_OptionalGroup) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_OptionalGroup.Unmarshal(m, b)
 }
@@ -1447,6 +1449,7 @@
 func (*FieldTestMessage_RequiredGroup) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0, 1}
 }
+
 func (m *FieldTestMessage_RequiredGroup) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_RequiredGroup.Unmarshal(m, b)
 }
@@ -1485,6 +1488,7 @@
 func (*FieldTestMessage_RepeatedGroup) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0, 2}
 }
+
 func (m *FieldTestMessage_RepeatedGroup) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_RepeatedGroup.Unmarshal(m, b)
 }
@@ -1523,6 +1527,7 @@
 func (*FieldTestMessage_OneofGroup) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0, 6}
 }
+
 func (m *FieldTestMessage_OneofGroup) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_OneofGroup.Unmarshal(m, b)
 }
@@ -1560,6 +1565,7 @@
 func (*FieldTestMessage_Message) Descriptor() ([]byte, []int) {
 	return fileDescriptor_fd8a9d72b841fd68, []int{0, 7}
 }
+
 func (m *FieldTestMessage_Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_Message.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/proto2/nested_messages.pb.go b/cmd/protoc-gen-go/testdata/proto2/nested_messages.pb.go
index f06711d..1daa2eb 100644
--- a/cmd/protoc-gen-go/testdata/proto2/nested_messages.pb.go
+++ b/cmd/protoc-gen-go/testdata/proto2/nested_messages.pb.go
@@ -34,6 +34,7 @@
 func (*Layer1) Descriptor() ([]byte, []int) {
 	return fileDescriptor_7417ee157699d191, []int{0}
 }
+
 func (m *Layer1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Layer1.Unmarshal(m, b)
 }
@@ -79,6 +80,7 @@
 func (*Layer1_Layer2) Descriptor() ([]byte, []int) {
 	return fileDescriptor_7417ee157699d191, []int{0, 0}
 }
+
 func (m *Layer1_Layer2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Layer1_Layer2.Unmarshal(m, b)
 }
@@ -116,6 +118,7 @@
 func (*Layer1_Layer2_Layer3) Descriptor() ([]byte, []int) {
 	return fileDescriptor_7417ee157699d191, []int{0, 0, 0}
 }
+
 func (m *Layer1_Layer2_Layer3) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Layer1_Layer2_Layer3.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/proto2/proto2.pb.go b/cmd/protoc-gen-go/testdata/proto2/proto2.pb.go
index 1812234..a912199 100644
--- a/cmd/protoc-gen-go/testdata/proto2/proto2.pb.go
+++ b/cmd/protoc-gen-go/testdata/proto2/proto2.pb.go
@@ -34,6 +34,7 @@
 func (*Message) Descriptor() ([]byte, []int) {
 	return fileDescriptor_d756bbe8817c03c1, []int{0}
 }
+
 func (m *Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Message.Unmarshal(m, b)
 }
diff --git a/cmd/protoc-gen-go/testdata/proto3/fields.pb.go b/cmd/protoc-gen-go/testdata/proto3/fields.pb.go
index 26d8165..92d9e23 100644
--- a/cmd/protoc-gen-go/testdata/proto3/fields.pb.go
+++ b/cmd/protoc-gen-go/testdata/proto3/fields.pb.go
@@ -74,6 +74,7 @@
 func (*FieldTestMessage) Descriptor() ([]byte, []int) {
 	return fileDescriptor_f1e3ea068187307c, []int{0}
 }
+
 func (m *FieldTestMessage) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage.Unmarshal(m, b)
 }
@@ -244,6 +245,7 @@
 func (*FieldTestMessage_Message) Descriptor() ([]byte, []int) {
 	return fileDescriptor_f1e3ea068187307c, []int{0, 3}
 }
+
 func (m *FieldTestMessage_Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_Message.Unmarshal(m, b)
 }
diff --git a/protogen/protogen.go b/protogen/protogen.go
index ae31fd2..753325e 100644
--- a/protogen/protogen.go
+++ b/protogen/protogen.go
@@ -348,6 +348,7 @@
 	GoImportPath  GoImportPath  // import path of this file's Go package
 	Messages      []*Message    // top-level message declarations
 	Enums         []*Enum       // top-level enum declarations
+	Extensions    []*Extension  // top-level extension declarations
 	Generate      bool          // true if we should generate code for this file
 
 	// GeneratedFilenamePrefix is used to construct filenames for generated
@@ -397,8 +398,18 @@
 	for i, edescs := 0, desc.Enums(); i < edescs.Len(); i++ {
 		f.Enums = append(f.Enums, newEnum(gen, f, nil, edescs.Get(i)))
 	}
+	for i, extdescs := 0, desc.Extensions(); i < extdescs.Len(); i++ {
+		f.Extensions = append(f.Extensions, newField(gen, f, nil, extdescs.Get(i)))
+	}
 	for _, message := range f.Messages {
-		message.init(gen)
+		if err := message.init(gen); err != nil {
+			return nil, err
+		}
+	}
+	for _, extension := range f.Extensions {
+		if err := extension.init(gen); err != nil {
+			return nil, err
+		}
 	}
 	return f, nil
 }
@@ -427,12 +438,13 @@
 type Message struct {
 	Desc protoreflect.MessageDescriptor
 
-	GoIdent  GoIdent    // name of the generated Go type
-	Fields   []*Field   // message field declarations
-	Oneofs   []*Oneof   // oneof declarations
-	Messages []*Message // nested message declarations
-	Enums    []*Enum    // nested enum declarations
-	Path     []int32    // location path of this message
+	GoIdent    GoIdent      // name of the generated Go type
+	Fields     []*Field     // message field declarations
+	Oneofs     []*Oneof     // oneof declarations
+	Messages   []*Message   // nested message declarations
+	Enums      []*Enum      // nested enum declarations
+	Extensions []*Extension // nested extension declarations
+	Path       []int32      // location path of this message
 }
 
 func newMessage(gen *Plugin, f *File, parent *Message, desc protoreflect.MessageDescriptor) *Message {
@@ -460,6 +472,9 @@
 	for i, fdescs := 0, desc.Fields(); i < fdescs.Len(); i++ {
 		message.Fields = append(message.Fields, newField(gen, f, message, fdescs.Get(i)))
 	}
+	for i, extdescs := 0, desc.Extensions(); i < extdescs.Len(); i++ {
+		message.Extensions = append(message.Extensions, newField(gen, f, message, extdescs.Get(i)))
+	}
 
 	// Field name conflict resolution.
 	//
@@ -524,6 +539,11 @@
 	for _, oneof := range message.Oneofs {
 		oneof.init(gen, message)
 	}
+	for _, extension := range message.Extensions {
+		if err := extension.init(gen); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
@@ -536,19 +556,29 @@
 	// '{{GoName}}' and a getter method named 'Get{{GoName}}'.
 	GoName string
 
-	ContainingType *Message // message in which this field occurs
-	MessageType    *Message // type for message or group fields; nil otherwise
-	EnumType       *Enum    // type for enum fields; nil otherwise
-	OneofType      *Oneof   // containing oneof; nil if not part of a oneof
-	Path           []int32  // location path of this field
+	ParentMessage *Message // message in which this field is defined; nil if top-level extension
+	ExtendedType  *Message // extended message for extension fields; nil otherwise
+	MessageType   *Message // type for message or group fields; nil otherwise
+	EnumType      *Enum    // type for enum fields; nil otherwise
+	OneofType     *Oneof   // containing oneof; nil if not part of a oneof
+	Path          []int32  // location path of this field
 }
 
 func newField(gen *Plugin, f *File, message *Message, desc protoreflect.FieldDescriptor) *Field {
+	var path []int32
+	switch {
+	case desc.ExtendedType() != nil && message == nil:
+		path = []int32{fileExtensionField, int32(desc.Index())}
+	case desc.ExtendedType() != nil && message != nil:
+		path = pathAppend(message.Path, messageExtensionField, int32(desc.Index()))
+	default:
+		path = pathAppend(message.Path, messageFieldField, int32(desc.Index()))
+	}
 	field := &Field{
-		Desc:           desc,
-		GoName:         camelCase(string(desc.Name())),
-		ContainingType: message,
-		Path:           pathAppend(message.Path, messageFieldField, int32(desc.Index())),
+		Desc:          desc,
+		GoName:        camelCase(string(desc.Name())),
+		ParentMessage: message,
+		Path:          path,
 	}
 	if desc.OneofType() != nil {
 		field.OneofType = message.Oneofs[desc.OneofType().Index()]
@@ -556,6 +586,9 @@
 	return field
 }
 
+// Extension is an alias of Field for documentation.
+type Extension = Field
+
 func (field *Field) init(gen *Plugin) error {
 	desc := field.Desc
 	switch desc.Kind() {
@@ -574,6 +607,14 @@
 		}
 		field.EnumType = enum
 	}
+	if desc.ExtendedType() != nil {
+		mname := desc.ExtendedType().FullName()
+		message, ok := gen.messagesByName[mname]
+		if !ok {
+			return fmt.Errorf("field %v: no descriptor for type %v", desc.FullName(), mname)
+		}
+		field.ExtendedType = message
+	}
 	return nil
 }
 
@@ -581,18 +622,18 @@
 type Oneof struct {
 	Desc protoreflect.OneofDescriptor
 
-	GoName         string   // Go field name of this oneof
-	ContainingType *Message // message in which this oneof occurs
-	Fields         []*Field // fields that are part of this oneof
-	Path           []int32  // location path of this oneof
+	GoName        string   // Go field name of this oneof
+	ParentMessage *Message // message in which this oneof occurs
+	Fields        []*Field // fields that are part of this oneof
+	Path          []int32  // location path of this oneof
 }
 
 func newOneof(gen *Plugin, f *File, message *Message, desc protoreflect.OneofDescriptor) *Oneof {
 	return &Oneof{
-		Desc:           desc,
-		ContainingType: message,
-		GoName:         camelCase(string(desc.Name())),
-		Path:           pathAppend(message.Path, messageOneofField, int32(desc.Index())),
+		Desc:          desc,
+		ParentMessage: message,
+		GoName:        camelCase(string(desc.Name())),
+		Path:          pathAppend(message.Path, messageOneofField, int32(desc.Index())),
 	}
 }
 
@@ -782,14 +823,16 @@
 // See descriptor.proto for more information about this.
 const (
 	// field numbers in FileDescriptorProto
-	filePackageField = 2 // package
-	fileMessageField = 4 // message_type
-	fileEnumField    = 5 // enum_type
+	filePackageField   = 2 // package
+	fileMessageField   = 4 // message_type
+	fileEnumField      = 5 // enum_type
+	fileExtensionField = 7 // extension
 	// field numbers in DescriptorProto
-	messageFieldField   = 2 // field
-	messageMessageField = 3 // nested_type
-	messageEnumField    = 4 // enum_type
-	messageOneofField   = 8 // oneof_decl
+	messageFieldField     = 2 // field
+	messageMessageField   = 3 // nested_type
+	messageEnumField      = 4 // enum_type
+	messageExtensionField = 6 // extension
+	messageOneofField     = 8 // oneof_decl
 	// field numbers in EnumDescriptorProto
 	enumValueField = 2 // value
 )