Index: src/wp-includes/js/jquery/jquery.masonry.js
===================================================================
--- src/wp-includes/js/jquery/jquery.masonry.js	(revision 38254)
+++ src/wp-includes/js/jquery/jquery.masonry.js	(working copy)
@@ -26,7 +26,7 @@
     var isAniOption = this.options.isAnimated;
     if ( isAniOption !== undefined ) {
       this.options.transitionDuration = isAniOption ?
-        Masonry.prototype.options.transitionDuration : 0;
+        this.options.transitionDuration : 0;
     }
 
     if ( isAniOption === undefined || isAniOption ) {