diff --git a/codec.go b/codec.go
index 8de1b8b..dff9f60 100644
--- a/codec.go
+++ b/codec.go
@@ -93,10 +93,12 @@ func (jsonCodec) Marshal(v interface{}) ([]byte, error) {
 }
 
 func (jsonCodec) Unmarshal(data []byte, v interface{}) error {
+	if len(data) == 0 {
+		return nil
+	}
 	if pb, ok := v.(proto.Message); ok {
 		return jsonpb.Unmarshal(b.NewReader(data), pb)
 	}
-
 	return json.Unmarshal(data, v)
 }
 
diff --git a/grpc.go b/grpc.go
index 1113f84..874f727 100644
--- a/grpc.go
+++ b/grpc.go
@@ -203,9 +203,13 @@ func (g *grpcServer) handler(srv interface{}, stream grpc.ServerStream) error {
 
 	// get content type
 	ct := defaultContentType
+
 	if ctype, ok := md["x-content-type"]; ok {
 		ct = ctype
 	}
+	if ctype, ok := md["content-type"]; ok {
+		ct = ctype
+	}
 
 	delete(md, "x-content-type")
 	delete(md, "timeout")