diff --git a/core/misc/tabledrag.js b/core/misc/tabledrag.js
index 273dcc1..3d9cb94 100644
--- a/core/misc/tabledrag.js
+++ b/core/misc/tabledrag.js
@@ -610,7 +610,7 @@ Drupal.tableDrag.prototype.getMouseOffset = function (target, event) {
  */
 Drupal.tableDrag.prototype.findDropTargetRow = function (x, y) {
   var rows = $(this.table.tBodies[0].rows).not(':hidden');
-  for (var n = 0; n < rows.length; n++) {
+  for (var n = 0, len = rows.length; n < len; ++n) {
     var row = rows[n];
     var $row = $(row);
     var indentDiff = 0;