--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -1267,29 +1267,16 @@ toolbarpaletteitem[place="menu-panel"] >
   padding-inline-start: .5em;
 }
 
 .subviewbutton > .menu-iconic-left {
   -moz-appearance: none;
   margin-inline-end: 0;
 }
 
-%ifdef XP_WIN
-/* Overrides from menu.css to prevent items in the bookmarks popup from being too tall.
-   These won't be necessary once menu.css is loaded as a UA style (Bug 1420229). */
-#BMB_bookmarksPopup .subviewbutton > .menu-iconic-left {
-  padding-top: 0;
-  -moz-appearance: none;
-}
-
-#BMB_bookmarksPopup .subviewbutton {
-  -moz-appearance: none;
-}
-%endif
-
 menuitem[checked="true"].subviewbutton > .menu-iconic-left {
   visibility: hidden;
 }
 
 #PanelUI-panicView > .panel-subview-body,
 #PanelUI-panicView {
   overflow: visible;
 }