--- a/toolkit/themes/shared/media/videocontrols.css
+++ b/toolkit/themes/shared/media/videocontrols.css
@@ -76,20 +76,16 @@ audio > xul|videocontrols {
 .controlsSpacerStack {
   display: flex;
   flex-direction: column;
   flex-grow: 1;
   justify-content: center;
   align-items: center;
 }
 
-.controlsSpacer {
-  background-color: rgba(255,255,255,.4);
-}
-
 .controlBar {
   position: relative;
   display: flex;
   box-sizing: border-box;
   justify-content: center;
   align-items: center;
   overflow: hidden;
   height: 40px;