--- a/browser/components/places/content/sidebarUtils.js
+++ b/browser/components/places/content/sidebarUtils.js
@@ -1,14 +1,18 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
-window.top.gUIDensity.update();
+
+let uidensity = window.top.document.documentElement.getAttribute("uidensity");
+if (uidensity) {
+  document.documentElement.setAttribute("uidensity", uidensity);
+}
 
 var SidebarUtils = {
   handleTreeClick: function SU_handleTreeClick(aTree, aEvent, aGutterSelect) {
     // right-clicks are not handled here
     if (aEvent.button == 2)
       return;
 
     var tbo = aTree.treeBoxObject;