diff --git a/phpgwapi/js/jsapi/app_base.js b/phpgwapi/js/jsapi/app_base.js
index 851760d922..a264cad502 100644
--- a/phpgwapi/js/jsapi/app_base.js
+++ b/phpgwapi/js/jsapi/app_base.js
@@ -100,6 +100,7 @@ var AppJS = Class.extend(
 	 */
 	destroy: function() {
 		delete this.et2;
+		delete this.sidebox;
 		delete window.app[this.appname];
 	},