Index: src/wp-includes/js/mediaelement/wp-mediaelement.css
===================================================================
--- src/wp-includes/js/mediaelement/wp-mediaelement.css	(revision 30880)
+++ src/wp-includes/js/mediaelement/wp-mediaelement.css	(working copy)
@@ -13,6 +13,10 @@
 	background: #222;
 }
 
+.mejs-controls a.mejs-horizontal-volume-slider {
+	display: table;
+}
+
 .mejs-controls .mejs-time-rail .mejs-time-loaded,
 .mejs-controls .mejs-horizontal-volume-slider .mejs-horizontal-volume-current {
 	background: #fff;