diff --git a/src/org/redkale/convert/ConvertFactory.java b/src/org/redkale/convert/ConvertFactory.java
index 7f62a7d62..ecb958a54 100644
--- a/src/org/redkale/convert/ConvertFactory.java
+++ b/src/org/redkale/convert/ConvertFactory.java
@@ -211,7 +211,7 @@ public abstract class ConvertFactory<R extends Reader, W extends Writer> {
                 loaderInited.set(true);
             }
         }
-        return null;
+        return type == ConvertType.PROTOBUF ? defProtobufConvert : null;
     }
 
     public abstract ConvertType getConvertType();