--- a/browser/themes/shared/devedition.inc.css
+++ b/browser/themes/shared/devedition.inc.css
@@ -147,17 +147,17 @@
 
 #tabbrowser-tabs,
 #TabsToolbar,
 #browser-panel {
   background: var(--chrome-background-color);
   color: var(--chrome-color);
 }
 
-#navigator-toolbox::after {
+#navigator-toolbox:-moz-lwtheme::after {
   background: var(--chrome-navigator-toolbox-separator-color);
 }
 
 #navigator-toolbox > toolbar:not(#TabsToolbar):not(#toolbar-menubar),
 .browserContainer > findbar,
 #browser-bottombox {
   background-color: var(--chrome-secondary-background-color) !important;
   background-image: none !important;