diff --git a/dubbo-rpc/dubbo-rpc-dubbo/src/main/java/org/apache/dubbo/rpc/protocol/dubbo/DecodeableRpcResult.java b/dubbo-rpc/dubbo-rpc-dubbo/src/main/java/org/apache/dubbo/rpc/protocol/dubbo/DecodeableRpcResult.java
index fac7c64a6ca..0edfdb8f3a3 100644
--- a/dubbo-rpc/dubbo-rpc-dubbo/src/main/java/org/apache/dubbo/rpc/protocol/dubbo/DecodeableRpcResult.java
+++ b/dubbo-rpc/dubbo-rpc-dubbo/src/main/java/org/apache/dubbo/rpc/protocol/dubbo/DecodeableRpcResult.java
@@ -97,7 +97,7 @@ public Object decode(Channel channel, InputStream input) throws IOException {
                 handleAttachment(in);
                 break;
             default:
-                throw new IOException("Unknown result flag, expect '0' '1' '2', get " + flag);
+                throw new IOException("Unknown result flag, expect '0' '1' '2' '3' '4' '5', but received: " + flag);
         }
         if (in instanceof Cleanable) {
             ((Cleanable) in).cleanup();