diff --git a/examples/helloworld/helloworld/helloworld.pb.go b/examples/helloworld/helloworld/helloworld.pb.go
index 1ff931a3..f9390dbc 100644
--- a/examples/helloworld/helloworld/helloworld.pb.go
+++ b/examples/helloworld/helloworld/helloworld.pb.go
@@ -84,9 +84,9 @@ func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
 	s.RegisterService(&_Greeter_serviceDesc, srv)
 }
 
-func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(HelloRequest)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(GreeterServer).SayHello(ctx, in)
diff --git a/examples/route_guide/routeguide/route_guide.pb.go b/examples/route_guide/routeguide/route_guide.pb.go
index fcf5c748..487a4dae 100644
--- a/examples/route_guide/routeguide/route_guide.pb.go
+++ b/examples/route_guide/routeguide/route_guide.pb.go
@@ -310,9 +310,9 @@ func RegisterRouteGuideServer(s *grpc.Server, srv RouteGuideServer) {
 	s.RegisterService(&_RouteGuide_serviceDesc, srv)
 }
 
-func _RouteGuide_GetFeature_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _RouteGuide_GetFeature_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(Point)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(RouteGuideServer).GetFeature(ctx, in)
diff --git a/health/grpc_health_v1alpha/health.pb.go b/health/grpc_health_v1alpha/health.pb.go
index c333a975..6b5ef31f 100644
--- a/health/grpc_health_v1alpha/health.pb.go
+++ b/health/grpc_health_v1alpha/health.pb.go
@@ -108,9 +108,9 @@ func RegisterHealthServer(s *grpc.Server, srv HealthServer) {
 	s.RegisterService(&_Health_serviceDesc, srv)
 }
 
-func _Health_Check_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _Health_Check_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(HealthCheckRequest)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(HealthServer).Check(ctx, in)
diff --git a/interop/grpc_testing/test.pb.go b/interop/grpc_testing/test.pb.go
index b25e98b8..26d1a44b 100755
--- a/interop/grpc_testing/test.pb.go
+++ b/interop/grpc_testing/test.pb.go
@@ -539,9 +539,9 @@ func RegisterTestServiceServer(s *grpc.Server, srv TestServiceServer) {
 	s.RegisterService(&_TestService_serviceDesc, srv)
 }
 
-func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(Empty)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(TestServiceServer).EmptyCall(ctx, in)
@@ -551,9 +551,9 @@ func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, codec
 	return out, nil
 }
 
-func _TestService_UnaryCall_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _TestService_UnaryCall_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(SimpleRequest)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(TestServiceServer).UnaryCall(ctx, in)
diff --git a/test/grpc_testing/test.pb.go b/test/grpc_testing/test.pb.go
index b25e98b8..26d1a44b 100644
--- a/test/grpc_testing/test.pb.go
+++ b/test/grpc_testing/test.pb.go
@@ -539,9 +539,9 @@ func RegisterTestServiceServer(s *grpc.Server, srv TestServiceServer) {
 	s.RegisterService(&_TestService_serviceDesc, srv)
 }
 
-func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(Empty)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(TestServiceServer).EmptyCall(ctx, in)
@@ -551,9 +551,9 @@ func _TestService_EmptyCall_Handler(srv interface{}, ctx context.Context, codec
 	return out, nil
 }
 
-func _TestService_UnaryCall_Handler(srv interface{}, ctx context.Context, codec grpc.Codec, buf []byte) (interface{}, error) {
+func _TestService_UnaryCall_Handler(srv interface{}, ctx context.Context, decodeFunc func(interface{}) error) (interface{}, error) {
 	in := new(SimpleRequest)
-	if err := codec.Unmarshal(buf, in); err != nil {
+	if err := decodeFunc(in); err != nil {
 		return nil, err
 	}
 	out, err := srv.(TestServiceServer).UnaryCall(ctx, in)