diff --git a/_conformance/conformance.go b/_conformance/conformance.go
new file mode 100644
index 0000000..c54212c
--- /dev/null
+++ b/_conformance/conformance.go
@@ -0,0 +1,161 @@
+// Go support for Protocol Buffers - Google's data interchange format
+//
+// Copyright 2016 The Go Authors.  All rights reserved.
+// https://github.com/golang/protobuf
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// conformance implements the conformance test subprocess protocol as
+// documented in conformance.proto.
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"os"
+
+	pb "github.com/golang/protobuf/_conformance/conformance_proto"
+	"github.com/golang/protobuf/jsonpb"
+	"github.com/golang/protobuf/proto"
+)
+
+func main() {
+	var sizeBuf [4]byte
+	inbuf := make([]byte, 0, 4096)
+	outbuf := proto.NewBuffer(nil)
+	for {
+		if _, err := io.ReadFull(os.Stdin, sizeBuf[:]); err == io.EOF {
+			break
+		} else if err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: read request:", err)
+			os.Exit(1)
+		}
+		size := binary.LittleEndian.Uint32(sizeBuf[:])
+		if int(size) > cap(inbuf) {
+			inbuf = make([]byte, size)
+		}
+		inbuf = inbuf[:size]
+		if _, err := io.ReadFull(os.Stdin, inbuf); err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: read request:", err)
+			os.Exit(1)
+		}
+
+		req := new(pb.ConformanceRequest)
+		if err := proto.Unmarshal(inbuf, req); err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: parse request:", err)
+			os.Exit(1)
+		}
+		res := handle(req)
+
+		if err := outbuf.Marshal(res); err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: marshal response:", err)
+			os.Exit(1)
+		}
+		binary.LittleEndian.PutUint32(sizeBuf[:], uint32(len(outbuf.Bytes())))
+		if _, err := os.Stdout.Write(sizeBuf[:]); err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: write response:", err)
+			os.Exit(1)
+		}
+		if _, err := os.Stdout.Write(outbuf.Bytes()); err != nil {
+			fmt.Fprintln(os.Stderr, "go conformance: write response:", err)
+			os.Exit(1)
+		}
+		outbuf.Reset()
+	}
+}
+
+var jsonMarshaler = jsonpb.Marshaler{
+	OrigName: true,
+}
+
+func handle(req *pb.ConformanceRequest) *pb.ConformanceResponse {
+	var err error
+	var msg pb.TestAllTypes
+	switch p := req.Payload.(type) {
+	case *pb.ConformanceRequest_ProtobufPayload:
+		err = proto.Unmarshal(p.ProtobufPayload, &msg)
+	case *pb.ConformanceRequest_JsonPayload:
+		err = jsonpb.UnmarshalString(p.JsonPayload, &msg)
+		if err != nil && err.Error() == "unmarshaling Any not supported yet" {
+			return &pb.ConformanceResponse{
+				Result: &pb.ConformanceResponse_Skipped{
+					Skipped: err.Error(),
+				},
+			}
+		}
+	default:
+		return &pb.ConformanceResponse{
+			Result: &pb.ConformanceResponse_RuntimeError{
+				RuntimeError: "unknown request payload type",
+			},
+		}
+	}
+	if err != nil {
+		return &pb.ConformanceResponse{
+			Result: &pb.ConformanceResponse_ParseError{
+				ParseError: err.Error(),
+			},
+		}
+	}
+	switch req.RequestedOutputFormat {
+	case pb.WireFormat_PROTOBUF:
+		p, err := proto.Marshal(&msg)
+		if err != nil {
+			return &pb.ConformanceResponse{
+				Result: &pb.ConformanceResponse_SerializeError{
+					SerializeError: err.Error(),
+				},
+			}
+		}
+		return &pb.ConformanceResponse{
+			Result: &pb.ConformanceResponse_ProtobufPayload{
+				ProtobufPayload: p,
+			},
+		}
+	case pb.WireFormat_JSON:
+		p, err := jsonMarshaler.MarshalToString(&msg)
+		if err != nil {
+			return &pb.ConformanceResponse{
+				Result: &pb.ConformanceResponse_SerializeError{
+					SerializeError: err.Error(),
+				},
+			}
+		}
+		return &pb.ConformanceResponse{
+			Result: &pb.ConformanceResponse_JsonPayload{
+				JsonPayload: p,
+			},
+		}
+	default:
+		return &pb.ConformanceResponse{
+			Result: &pb.ConformanceResponse_RuntimeError{
+				RuntimeError: "unknown output format",
+			},
+		}
+	}
+}