--- a/browser/base/content/browser-places.js
+++ b/browser/base/content/browser-places.js
@@ -97,19 +97,19 @@ var StarUI = {
           break;
         }
         switch (aEvent.keyCode) {
           case KeyEvent.DOM_VK_ESCAPE:
             if (!this._element("editBookmarkPanelContent").hidden)
               this.cancelButtonOnCommand();
             break;
           case KeyEvent.DOM_VK_RETURN:
-            if (aEvent.target.className == "expander-up" ||
-                aEvent.target.className == "expander-down" ||
-                aEvent.target.id == "editBMPanel_newFolderButton") {
+            if (aEvent.target.classList.contains("expander-up") ||
+                aEvent.target.classList.contains("expander-down") ||
+                aEvent.target.id == "editBMPanel_newFolderButton")  {
               //XXX Why is this necessary? The defaultPrevented check should
               //    be enough.
               break;
             }
             this.panel.hidePopup();
             break;
         }
         break;