--- a/browser/themes/shared/tabs.inc.css
+++ b/browser/themes/shared/tabs.inc.css
@@ -412,21 +412,16 @@
   border-image-slice: 1;
   /* The 1px border and negative margin may amount to a different number of
      device pixels (bug 477157), so we also set a width to match the margin. */
   width: 1px;
   box-sizing: border-box;
   opacity: 0.2;
 }
 
-#TabsToolbar[brighttext] > #tabbrowser-tabs > .tabbrowser-tab::before,
-#TabsToolbar[brighttext] > #tabbrowser-tabs > .tabbrowser-tab::after {
-  opacity: 0.4;
-}
-
 /* Also show separators beside the selected tab when dragging it. */
 #tabbrowser-tabs[movingtab] > .tabbrowser-tab[beforeselected]:not([last-visible-tab])::after,
 .tabbrowser-tab:not([selected]):not([afterselected-visible]):not([afterhovered]):not([first-visible-tab]):not(:hover)::before,
 #tabbrowser-tabs:not([overflow]) > .tabbrowser-tab[last-visible-tab]:not([selected]):not([beforehovered]):not(:hover)::after {
   content: "";
   display: -moz-box;
 }