diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/css/customize-preview.css
--- a/wp/wp-includes/css/customize-preview.css	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/css/customize-preview.css	Tue Dec 15 13:49:49 2020 +0100
@@ -41,7 +41,7 @@
 	height: 30px;
 	min-width: 30px;
 	min-height: 30px;
-	line-height: 1em !important;
+	line-height: 1 !important;
 	font-size: 18px;
 	z-index: 5;
 	background: #0085ba !important;