diff --git a/core/src/net/oschina/j2cache/util/FastjsonSerializer.java b/core/src/net/oschina/j2cache/util/FastjsonSerializer.java
index 6f80075607d789addc9a0e7312aa1a3ccda63ff5..81483d60a7a37bb8ffab9c6c15c919b7c1666c8e 100644
--- a/core/src/net/oschina/j2cache/util/FastjsonSerializer.java
+++ b/core/src/net/oschina/j2cache/util/FastjsonSerializer.java
@@ -33,7 +33,7 @@ public class FastjsonSerializer implements Serializer {
 
     @Override
     public byte[] serialize(Object obj) {
-        return JSON.toJSONString(obj, SerializerFeature.WriteClassName).getBytes();
+        return JSON.toJSONString(obj, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteClassName).getBytes();
     }
 
     @Override