Index: src/wp-admin/css/forms.css
===================================================================
--- src/wp-admin/css/forms.css	(revision 46287)
+++ src/wp-admin/css/forms.css	(working copy)
@@ -340,6 +340,10 @@
 	box-shadow: none;
 }
 
+.wp-admin select:disabled {
+	opacity: 0.5;
+}
+
 .wp-admin .button-cancel {
 	padding: 0 5px;
 	line-height: 2;