diff --git a/misc/tabledrag.js b/misc/tabledrag.js
index 99168215dea8df7f2443ac75361655d1ecd589fd..4ac37149c3e4ff5996ba121d51ace6b53a6f8301 100644
--- a/misc/tabledrag.js
+++ b/misc/tabledrag.js
@@ -1014,7 +1014,7 @@ Drupal.tableDrag.prototype.row.prototype.findSiblings = function(rowSettings) {
   var siblings = new Array();
   var directions = new Array('prev', 'next');
   var rowIndentation = this.indents;
-  for (var d in directions) {
+  for (var d = 0; d < directions.length; d++) {
     var checkRow = $(this.element)[directions[d]]();
     while (checkRow.length) {
       // Check that the sibling contains a similar target field.