diff --git a/policeSecurityServer/src/main/java/com/changhu/support/fastjson2/serializer/MinioPrefixSerializer.java b/policeSecurityServer/src/main/java/com/changhu/support/fastjson2/serializer/MinioPrefixSerializer.java
index 83bc2a5..1e6a48b 100644
--- a/policeSecurityServer/src/main/java/com/changhu/support/fastjson2/serializer/MinioPrefixSerializer.java
+++ b/policeSecurityServer/src/main/java/com/changhu/support/fastjson2/serializer/MinioPrefixSerializer.java
@@ -26,6 +26,6 @@ public class MinioPrefixSerializer implements ObjectWriter<String> {
         if (object instanceof String path && StrUtil.isNotEmpty(path)) {
             jsonWriter.writeString(minioPrefix + object);
         }
-        jsonWriter.writeNull();
+        jsonWriter.writeString("");
     }
 }