diff --git misc/tabledrag.js misc/tabledrag.js
index a6fa2e2..8222458 100644
--- misc/tabledrag.js
+++ misc/tabledrag.js
@@ -657,7 +657,7 @@ Drupal.tableDrag.prototype.updateField = function(changedRow, group) {
       // Use the first row in the table as source, because it's garanteed to
       // be at the root level. Find the first item, then compare this row
       // against it as a sibling.
-      sourceRow = $('tr.draggable:first').get(0);
+      sourceRow = $(this.table).find('tr.draggable:first').get(0);
       if (sourceRow == this.rowObject.element) {
         sourceRow = $(this.rowObject.group[this.rowObject.group.length - 1]).next('tr.draggable').get(0);
       }