--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -570,17 +570,16 @@
 #endif
 
 <deck flex="1" id="tab-view-deck">
 <vbox flex="1" id="browser-panel">
 
   <toolbox id="navigator-toolbox" mode="icons">
     <!-- Menu -->
     <toolbar type="menubar" id="toolbar-menubar" class="chromeclass-menubar" customizable="true"
-             defaultset="menubar-items"
              mode="icons" iconsize="small"
 #ifdef MENUBAR_CAN_AUTOHIDE
              toolbarname="&menubarCmd.label;"
              accesskey="&menubarCmd.accesskey;"
 #if defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_QT)
              autohide="true"
 #endif
 #endif
@@ -602,17 +601,16 @@
 
     <toolbar id="TabsToolbar"
              fullscreentoolbar="true"
              customizable="true"
              mode="icons"
              iconsize="small"
              aria-label="&tabsToolbar.label;"
              context="toolbar-context-menu"
-             defaultset="tabbrowser-tabs,new-tab-button,alltabs-button"
              collapsed="true">
 
 #if defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_QT)
       <hbox id="private-browsing-indicator"
             skipintoolbarset="true"/>
 #endif
 
       <tabs id="tabbrowser-tabs"
@@ -684,21 +682,16 @@
            Should you need to add items to the toolbar here, make sure to also add them
            to the default placements of buttons in CustomizableUI.jsm, so the
            customization code doesn't get confused.
       -->
     <toolbar id="nav-bar"
              aria-label="&navbarCmd.label;"
              fullscreentoolbar="true" mode="icons" customizable="true"
              iconsize="small"
-#ifdef MOZ_DEV_EDITION
-             defaultset="urlbar-container,search-container,developer-button,bookmarks-menu-button,downloads-button,home-button,loop-button"
-#else
-             defaultset="urlbar-container,search-container,bookmarks-menu-button,downloads-button,home-button,loop-button"
-#endif
              customizationtarget="nav-bar-customization-target"
              overflowable="true"
              overflowbutton="nav-bar-overflow-button"
              overflowtarget="widget-overflow-list"
              overflowpanel="widget-overflow"
              context="toolbar-context-menu">
 
       <hbox id="nav-bar-customization-target" flex="1">
@@ -989,17 +982,16 @@
     </toolbar>
 
     <toolbarset id="customToolbars" context="toolbar-context-menu"/>
 
     <toolbar id="PersonalToolbar"
              mode="icons" iconsize="small"
              class="chromeclass-directories"
              context="toolbar-context-menu"
-             defaultset="personal-bookmarks"
              toolbarname="&personalbarCmd.label;" accesskey="&personalbarCmd.accesskey;"
              collapsed="true"
              customizable="true">
       <toolbaritem id="personal-bookmarks"
                    title="&bookmarksToolbarItem.label;"
                    cui-areatype="toolbar"
                    removable="true">
         <toolbarbutton id="bookmarks-toolbar-placeholder"

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1828,17 +1828,17 @@ BrowserGlue.prototype = {
     var notifyBox = win.gBrowser.getNotificationBox();
     var notification = notifyBox.appendNotification(text, title, null,
                                                     notifyBox.PRIORITY_CRITICAL_MEDIUM,
                                                     buttons);
     notification.persistence = -1; // Until user closes it
   },
 
   _migrateUI: function BG__migrateUI() {
-    const UI_VERSION = 38;
+    const UI_VERSION = 39;
     const BROWSER_DOCURL = "chrome://browser/content/browser.xul";
 
     let currentUIVersion;
     if (Services.prefs.prefHasUserValue("browser.migration.version")) {
       currentUIVersion = Services.prefs.getIntPref("browser.migration.version");
     } else {
       // This is a new profile, nothing to migrate.
       Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
@@ -2197,16 +2197,25 @@ BrowserGlue.prototype = {
 
     if (currentUIVersion < 37) {
       Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
     }
 
     if (currentUIVersion < 38) {
       LoginHelper.removeLegacySignonFiles();
     }
+
+    if (currentUIVersion < 39) {
+      // Remove the 'defaultset' value for all the toolbars
+      let toolbars = ["nav-bar", "PersonalToolbar",
+                      "addon-bar", "TabsToolbar", "toolbar-menubar"];
+      for (let toolbarId of toolbars) {
+        xulStore.removeValue(BROWSER_DOCURL, toolbarId, "defaultset");
+      }
+    }
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },
 
   _hasExistingNotificationPermission: function BG__hasExistingNotificationPermission() {
     let enumerator = Services.perms.enumerator;
     while (enumerator.hasMoreElements()) {
       let permission = enumerator.getNext().QueryInterface(Ci.nsIPermission);