diff --git a/adaptor.go b/adaptor_go1_12.go
similarity index 99%
rename from adaptor.go
rename to adaptor_go1_12.go
index 4317f24..6b9f2f0 100644
--- a/adaptor.go
+++ b/adaptor_go1_12.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.13
+
 package xerrors
 
 import (
diff --git a/adaptor_go1_13.go b/adaptor_go1_13.go
new file mode 100644
index 0000000..57f519d
--- /dev/null
+++ b/adaptor_go1_13.go
@@ -0,0 +1,55 @@
+// 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.
+
+// +build go1.13
+
+package xerrors
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+)
+
+// A Frame contains part of a call stack.
+type Frame = errors.Frame
+
+// Caller returns a Frame that describes a frame on the caller's stack.
+// The argument skip is the number of frames to skip over.
+// Caller(0) returns the frame for the caller of Caller.
+var Caller func(skip int) Frame = errors.Caller
+
+// FormatError calls the FormatError method of f with an errors.Printer
+// configured according to s and verb, and writes the result to s.
+func FormatError(f Formatter, s fmt.State, verb rune) {
+	// Assuming this function is only called from the Format method, and given
+	// that FormatError takes precedence over Format, it cannot be called from
+	// any package that supports errors.Formatter. It is therefore safe to
+	// disregard that State may be a specific printer implementation and use one
+	// of our choice instead.
+
+	width, okW := s.Width()
+	prec, okP := s.Precision()
+
+	// Construct format string from State s.
+	format := []byte{'%'}
+	if s.Flag('-') {
+		format = append(format, '-')
+	}
+	if s.Flag('+') {
+		format = append(format, '+')
+	}
+	if s.Flag(' ') {
+		format = append(format, ' ')
+	}
+	if okW {
+		format = strconv.AppendInt(format, int64(width), 10)
+	}
+	if okP {
+		format = append(format, '.')
+		format = strconv.AppendInt(format, int64(prec), 10)
+	}
+	format = append(format, string(verb)...)
+	fmt.Fprintf(s, string(format), f)
+}
diff --git a/fmt_test.go b/fmt_test.go
index 6744b8a..5933f18 100644
--- a/fmt_test.go
+++ b/fmt_test.go
@@ -7,7 +7,6 @@
 import (
 	"fmt"
 	"io"
-	"os"
 	"path"
 	"reflect"
 	"regexp"
@@ -91,7 +90,7 @@
 		nonascii = &wrapped{"café", nil}
 		newline  = &wrapped{"msg with\nnewline",
 			&wrapped{"and another\none", nil}}
-		fallback  = &wrapped{"fallback", os.ErrNotExist}
+		fallback  = &wrapped{"fallback", xerrors.New("file does not exist")}
 		oldAndNew = &wrapped{"new style", formatError("old style")}
 		framed    = &withFrameAndMore{
 			frame: xerrors.Caller(0),
@@ -106,6 +105,13 @@
 		want   string
 		regexp bool
 	}{{
+		err: xerrors.New("foo"),
+		fmt: "%+v",
+		want: "foo:" +
+			"\n    golang.org/x/xerrors_test.TestErrorFormatter" +
+			"\n        .+/golang.org/x/xerrors/fmt_test.go:1\\d\\d",
+		regexp: true,
+	}, {
 		err:  simple,
 		fmt:  "%s",
 		want: "simple",
@@ -156,7 +162,7 @@
 		fmt: "%+v",
 		want: "something:" +
 			"\n    golang.org/x/xerrors_test.TestErrorFormatter" +
-			"\n        .+/fmt_test.go:97" +
+			"\n        .+/fmt_test.go:9\\d" +
 			"\n    something more",
 		regexp: true,
 	}, {
@@ -173,7 +179,10 @@
 		// Note: no colon after the last error, as there are no details.
 		want: "fallback:" +
 			"\n    somefile.go:123" +
-			"\n  - file does not exist",
+			"\n  - file does not exist:" +
+			"\n    golang.org/x/xerrors_test.TestErrorFormatter" +
+			"\n        .+/golang.org/x/xerrors/fmt_test.go:9\\d",
+		regexp: true,
 	}, {
 		err:  opaque,
 		fmt:  "%s",
@@ -281,12 +290,12 @@
 		err:  simple,
 		fmt:  "%T",
 		want: "*xerrors_test.wrapped",
-	}, {
-		err:  simple,
-		fmt:  "%🤪",
-		want: "%!🤪(*xerrors_test.wrapped)",
-		// For 1.13:
-		//  want: "%!🤪(*xerrors_test.wrapped=&{simple <nil>})",
+		// }, {
+		// 	// The behavior for this case is different between go1.12 and go1.13.
+		// 	err:  simple,
+		// 	fmt:  "%🤪",
+		// 	want: "%!🤪(*xerrors_test.wrapped=&{simple <nil>})", // go1.12
+		// 	want: "&{%!🤪(string=simple) <nil>}",                // go1.13
 	}, {
 		err:  formatError("use fmt.Formatter"),
 		fmt:  "%#v",
diff --git a/format.go b/format_go1_12.go
similarity index 97%
rename from format.go
rename to format_go1_12.go
index 1bc9c26..ba856fe 100644
--- a/format.go
+++ b/format_go1_12.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.13
+
 package xerrors
 
 // A Formatter formats error messages.
diff --git a/format_go1_13.go b/format_go1_13.go
new file mode 100644
index 0000000..95c6596
--- /dev/null
+++ b/format_go1_13.go
@@ -0,0 +1,19 @@
+// 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.
+
+// +build go1.13
+
+package xerrors
+
+import "errors"
+
+// A Formatter formats error messages.
+type Formatter = errors.Formatter
+
+// A Printer formats error messages.
+//
+// The most common implementation of Printer is the one provided by package fmt
+// during Printf (as of Go 1.13). Localization packages such as golang.org/x/text/message
+// typically provide their own implementations.
+type Printer = errors.Printer
diff --git a/frame.go b/frame_go1_12.go
similarity index 98%
rename from frame.go
rename to frame_go1_12.go
index 0de628e..6740f7f 100644
--- a/frame.go
+++ b/frame_go1_12.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.13
+
 package xerrors
 
 import (