--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -746,17 +746,20 @@ toolbaritem[cui-areatype="menu-panel"][s
   padding-inline-start: 10px;
 }
 
 .panel-banner-item > .toolbarbutton-text {
   width: 0; /* Fancy cropping solution for flexbox. */
 }
 
 /* FxAccount indicator bits. */
-#appMenu-fxa-container:not([fxastatus="signedin"]) {
+
+/* Add the .toolbaritem-combined-buttons class to increase the specificity so as
+ * to override the end margin for .toolbaritem-combined-buttons items further down. */
+#appMenu-fxa-container.toolbaritem-combined-buttons:not([fxastatus="signedin"]) {
   margin-inline-end: 0;
 }
 
 #appMenu-fxa-label,
 #appMenu-fxa-icon {
   -moz-image-region: rect(0, 16px, 16px, 0);
   list-style-image: url(chrome://browser/skin/sync-horizontalbar.png);
 }