diff --git a/internal/impl/validate.go b/internal/impl/validate.go
index 0c32026..e210086 100644
--- a/internal/impl/validate.go
+++ b/internal/impl/validate.go
@@ -353,7 +353,7 @@
 
 			switch wtyp {
 			case wire.VarintType:
-				if len(b) >= 9 {
+				if len(b) >= 10 {
 					switch {
 					case b[0] < 0x80:
 						b = b[1:]
diff --git a/proto/testmessages_test.go b/proto/testmessages_test.go
index 3847c21..7a2eaad 100644
--- a/proto/testmessages_test.go
+++ b/proto/testmessages_test.go
@@ -1853,6 +1853,17 @@
 			pack.Raw("\xff\xff\xff\xff\xff\xff\xff\xff\xff\x02"),
 		}.Marshal(),
 	},
+	{
+		desc: "varint length overrun",
+		decodeTo: []proto.Message{
+			(*testpb.TestAllTypes)(nil),
+			(*testpb.TestAllExtensions)(nil),
+		},
+		wire: pack.Message{
+			pack.Tag{1, pack.VarintType},
+			pack.Raw("\xff\xff\xff\xff\xff\xff\xff\xff\xff"),
+		}.Marshal(),
+	},
 }
 
 type filterResolver struct {