--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -810,21 +810,21 @@ menuitem:not([type]):not(.menuitem-toolt
 #restore-button {
   list-style-image: url("chrome://global/skin/icons/Restore.gif");
 }
 #close-button {
   list-style-image: url("chrome://global/skin/icons/Close.gif");
 }
 
 /* Location bar */
-#nav-bar {
+#main-window {
   --urlbar-border-color: ThreeDShadow;
 }
 
-#nav-bar:-moz-lwtheme {
+#main-window:-moz-lwtheme {
   --urlbar-border-color: rgba(0,0,0,.3);
 }
 
 #urlbar,
 .searchbar-textbox {
   -moz-appearance: none;
   padding: 0;
   border: 1px solid var(--urlbar-border-color);

--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -1091,37 +1091,37 @@ toolbar[brighttext] .toolbarbutton-1 > .
   #restore-button:-moz-locale-dir(rtl),
   #close-button:-moz-locale-dir(rtl) {
     transform: scaleX(-1);
   }
 }
 
 /* ::::: Location Bar ::::: */
 
-#nav-bar {
+#main-window {
   --urlbar-border-color: ThreeDShadow;
   --urlbar-border-color-hover: var(--urlbar-border-color);
 }
 
-#nav-bar:-moz-lwtheme {
+#main-window:-moz-lwtheme {
   --urlbar-border-color: var(--toolbarbutton-hover-bordercolor);
 }
 
 @media (-moz-windows-default-theme) {
   @media (-moz-os-version: windows-vista),
          (-moz-os-version: windows-win7),
          (-moz-os-version: windows-win8) {
-    #nav-bar:not(:-moz-lwtheme) {
+    #main-window:not(:-moz-lwtheme) {
       --urlbar-border-color: hsla(210,54%,20%,.25) hsla(210,54%,20%,.27) hsla(210,54%,20%,.3);
       --urlbar-border-color-hover: hsla(210,54%,20%,.35) hsla(210,54%,20%,.37) hsla(210,54%,20%,.4);
     }
   }
 
   @media (-moz-os-version: windows-win10) {
-    #nav-bar:not(:-moz-lwtheme) {
+    #main-window:not(:-moz-lwtheme) {
       --urlbar-border-color: hsl(0,0%,90%);
       --urlbar-border-color-hover: hsl(0,0%,80%);
     }
   }
 }
 
 #urlbar,
 .searchbar-textbox {