--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -543,20 +543,20 @@
              aria-label="&navbarCmd.label;"
              fullscreentoolbar="true" mode="icons" customizable="true"
              iconsize="large"
              defaultset="urlbar-container,search-container,webrtc-status-button,bookmarks-menu-button,downloads-button,home-button,social-share-button,social-toolbar-item"
              customizationtarget="nav-bar-customizationtarget"
              overflowable="true"
              overflowbutton="nav-bar-overflow-button"
              overflowtarget="widget-overflow-list"
-             flex="501"
+             flex="1"
              context="toolbar-context-menu">
 
-      <hbox id="nav-bar-customizationtarget" class="customization-target" flex="1">
+      <hbox id="nav-bar-customizationtarget" class="customization-target" flex="501">
         <toolbaritem id="urlbar-container" align="center" flex="400" persist="width"
                      forwarddisabled="true" title="&locationItem.title;" removable="false"
                      customizableui-areatype="toolbar"
                      class="chromeclass-location" overflows="false">
           <toolbarbutton id="back-button" class="toolbarbutton-1 chromeclass-toolbar-additional"
                          label="&backCmd.label;"
                          command="Browser:BackOrBackDuplicate"
                          onclick="checkForMiddleClick(this, event);"