diff --git a/src/wp-includes/js/tinymce/skins/wordpress/wp-content.css b/src/wp-includes/js/tinymce/skins/wordpress/wp-content.css
index 96fed744df..9cd5c944b8 100644
--- a/src/wp-includes/js/tinymce/skins/wordpress/wp-content.css
+++ b/src/wp-includes/js/tinymce/skins/wordpress/wp-content.css
@@ -366,6 +366,11 @@ audio {
 	}
 }
 
+.wpview-wrap .wpview-content > iframe {
+	max-width: 100%;
+	background: transparent;
+}
+
 #wp-image-toolbar {
 	position: absolute;
 	margin: 0;