diff --git a/src/wp-includes/js/mce-view.js b/src/wp-includes/js/mce-view.js
index 4a7b96b1c6..98174543b0 100644
--- a/src/wp-includes/js/mce-view.js
+++ b/src/wp-includes/js/mce-view.js
@@ -478,8 +478,8 @@ window.wp = window.wp || {};
 					), function( link ) {
 						if (
 							link.href &&
-							link.href.indexOf( 'skins/lightgray/content.min.css' ) >= 0 &&
-							link.href.indexOf( 'skins/wordpress/wp-content.css' ) >= 0
+							link.href.indexOf( 'skins/lightgray/content.min.css' ) === -1 &&
+							link.href.indexOf( 'skins/wordpress/wp-content.css' ) === -1
 						) {
 							styles += dom.getOuterHTML( link );
 						}