diff --git a/apps/api/documents/api.js b/apps/api/documents/api.js
index 82f7a1341..f6b80edef 100644
--- a/apps/api/documents/api.js
+++ b/apps/api/documents/api.js
@@ -285,7 +285,7 @@
                             _onAppReady();
                         }
 
-                        if (handler) {
+                        if (handler && typeof handler == "function") {
                             res = handler.call(_self, {target: _self, data: msg.data});
                         }
                     }