diff --git a/protocol/json/client.go b/protocol/json/client.go
index 5fa8d82..f6555eb 100644
--- a/protocol/json/client.go
+++ b/protocol/json/client.go
@@ -86,7 +86,7 @@ type ClientMessageCodec struct {
 	codec codec.Codec
 }
 
-func (ccm *ClientMessageCodec) MessageType() MessageType {
+func (ccm *ClientMessageCodec) MessageType() protocol.MessageType {
 	return ccm.msg.MessageType
 }