diff --git a/wp-admin/js/custom-header.js b/wp-admin/js/custom-header.js
index fa7f1e4f88..aabd7d9c01 100644
--- a/wp-admin/js/custom-header.js
+++ b/wp-admin/js/custom-header.js
@@ -8,7 +8,8 @@
 
 		$headers.imagesLoaded( function() {
 			$headers.masonry({
-				itemSelector: '.default-header'
+				itemSelector: '.default-header',
+				isRTL: !! ( 'undefined' != typeof isRtl && isRtl )
 			});
 		});