diff --git src/wp-admin/css/customize-controls.css src/wp-admin/css/customize-controls.css
index b35bc3b..7ba16c9 100644
--- src/wp-admin/css/customize-controls.css
+++ src/wp-admin/css/customize-controls.css
@@ -160,6 +160,7 @@ body {
 #customize-theme-controls .accordion-section-content {
 	color: #555;
 	background: transparent;
+	overflow: hidden;
 }
 
 #customize-controls .control-section:hover > .accordion-section-title,