diff --git src/wp-includes/js/jquery/jquery.masonry.js src/wp-includes/js/jquery/jquery.masonry.js
index aceb766..f01d54a 100644
--- src/wp-includes/js/jquery/jquery.masonry.js
+++ src/wp-includes/js/jquery/jquery.masonry.js
@@ -26,7 +26,7 @@
     var isAniOption = this.options.isAnimated;
     if ( isAniOption !== undefined ) {
       this.options.transitionDuration = isAniOption ?
-        Masonry.prototype.options.transitionDuration : 0;
+        '0.4s' : 0;
     }
 
     if ( isAniOption === undefined || isAniOption ) {