diff --git a/lib/yui/formautosubmit/formautosubmit.js b/lib/yui/formautosubmit/formautosubmit.js
index 39525dbf9d1..23d74c94a0e 100644
--- a/lib/yui/formautosubmit/formautosubmit.js
+++ b/lib/yui/formautosubmit/formautosubmit.js
@@ -66,8 +66,8 @@ YUI.add('moodle-core-formautosubmit',
                 var startindex = select.getData('startindex');
                 var currentindex = select.get('selectedIndex');
 
-                var previousindex = select.getAttribute('data-previousindex');
-                select.setAttribute('data-previousindex', currentindex);
+                var previousindex = parseInt(select.getData('previousindex'), 10);
+                select.setData('previousindex', currentindex);
                 if (!previousindex) {
                     previousindex = startindex;
                 }