diff --git a/android/src/main/java/com/finogeeks/mop/api/mop/BaseModule.java b/android/src/main/java/com/finogeeks/mop/api/mop/BaseModule.java
index 6c95d06..1694dbd 100644
--- a/android/src/main/java/com/finogeeks/mop/api/mop/BaseModule.java
+++ b/android/src/main/java/com/finogeeks/mop/api/mop/BaseModule.java
@@ -59,7 +59,7 @@ public class BaseModule extends BaseApi {
         if (disablePermission == null) {
             disablePermission = false;
         }
-        String userId = null;
+        String userId = "";
         if (param.get("userId") != null) {
             userId = (String) param.get("userId");
         }