--- a/browser/themes/shared/compacttheme.inc.css
+++ b/browser/themes/shared/compacttheme.inc.css
@@ -131,21 +131,16 @@ toolbar[brighttext] .toolbarbutton-1 {
 #urlbar-zoom-button:-moz-lwtheme-brighttext:hover {
   background-color: rgba(255,255,255,.2);
 }
 
 #urlbar-zoom-button:-moz-lwtheme-brighttext:hover:active {
   background-color: rgba(255,255,255,.3);
 }
 
-/* Use smaller back button icon */
-#back-button {
-  list-style-image: url("chrome://browser/skin/back.svg");
-}
-
 .tab-throbber[selected][progress] {
   list-style-image: url("chrome://browser/skin/compacttheme/loading-inverted.png");
 }
 
 @media (min-resolution: 1.1dppx) {
   .tab-throbber[selected][progress] {
     list-style-image: url("chrome://browser/skin/compacttheme/loading-inverted@2x.png");
   }