diff --git a/src/wp-admin/css/customize-controls.css b/src/wp-admin/css/customize-controls.css
index 1d69609d58..36e512aa01 100644
--- a/src/wp-admin/css/customize-controls.css
+++ b/src/wp-admin/css/customize-controls.css
@@ -613,6 +613,9 @@ p.customize-section-description {
 	height: 100%;
 	position: absolute;
 }
+#customize-preview iframe + iframe {
+	visibility: hidden;
+}
 
 .wp-full-overlay-sidebar {
 	background: #eee;