diff --git a/js/ui/notificationDaemon.js b/js/ui/notificationDaemon.js
index ed8870fe1..84bfec466 100644
--- a/js/ui/notificationDaemon.js
+++ b/js/ui/notificationDaemon.js
@@ -687,6 +687,8 @@ var GtkNotificationDaemonAppSource = new Lang.Class({
     _init: function(appId) {
         this._appId = appId;
         this._objectPath = objectPathFromAppId(appId);
+        if (!GLib.Variant.is_object_path(this._objectPath))
+            throw new InvalidAppError();
 
         this._app = Shell.AppSystem.get_default().lookup_app(appId + '.desktop');
         if (!this._app)