diff --git a/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DecodeableRpcInvocation.java b/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DecodeableRpcInvocation.java
index a1dbd660a66..8c1e46759c4 100644
--- a/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DecodeableRpcInvocation.java
+++ b/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DecodeableRpcInvocation.java
@@ -103,11 +103,7 @@ public Object decode(Channel channel, InputStream input) throws IOException {
                 Class<?>[] pts;
 
                 // NOTICE modified by lishen
-                int argNum = -1;
-
-                if (CodecSupport.getSerialization(channel.getUrl(), serializationType) instanceof OptimizedSerialization) {
-                    argNum = in.readInt();
-                }
+                int argNum = in.readInt();
                 if (argNum >= 0) {
                     if (argNum == 0) {
                         pts = DubboCodec.EMPTY_CLASS_ARRAY;
diff --git a/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java b/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java
index 6b588190b60..3e5fd8944f1 100644
--- a/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java
+++ b/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java
@@ -181,15 +181,13 @@ protected void encodeRequestData(Channel channel, ObjectOutput out, Object data)
 
         // NOTICE modified by lishen
         // TODO
-        if (getSerialization(channel) instanceof OptimizedSerialization) {
-            if (!containComplexArguments(inv)) {
-                out.writeInt(inv.getParameterTypes().length);
-            } else {
-                out.writeInt(-1);
-            }
+        if (getSerialization(channel) instanceof OptimizedSerialization && !containComplexArguments(inv)) {
+            out.writeInt(inv.getParameterTypes().length);
         } else {
+            out.writeInt(-1);
             out.writeUTF(ReflectUtils.getDesc(inv.getParameterTypes()));
         }
+
         Object[] args = inv.getArguments();
         if (args != null)
             for (int i = 0; i < args.length; i++){