diff --git a/frontend-js/src/main/js/GuiConnector.js b/frontend-js/src/main/js/GuiConnector.js
index 296b0bf84f5414856895f94a260bbb674ec2731b..b8846648b2a98bb1cb440d809231697fcb9dbb85 100644
--- a/frontend-js/src/main/js/GuiConnector.js
+++ b/frontend-js/src/main/js/GuiConnector.js
@@ -133,7 +133,7 @@ GuiConnector.showProcessing = function(messageText) {
       width : "150px",
       closeOnEscape : false,
       open : function(event, ui) {
-        $(".ui-dialog-titlebar-close", ui).hide();
+        $(".ui-dialog-titlebar-close", ui.dialog | ui).hide();
       },
     });
   }