diff --git a/admin/cron.php b/admin/cron.php
index 574886e632d..b6e6a81b91d 100644
--- a/admin/cron.php
+++ b/admin/cron.php
@@ -103,9 +103,9 @@
         /// Delete duplicate enrolments (don't know what causes these yet - expired sessions?)
     
         if ($users = get_records_select("user_students", "userid > 0 GROUP BY course, userid ".
-                                        "HAVING count(*) > 1", "", "*,count(*)")) {
+                                        "HAVING count(*) > 1", "", "max(id) as id, userid, course ,count(*)")) {
             foreach ($users as $user) {
-               delete_records_select("user_students", "userid = '$user->userid' ".
+                delete_records_select("user_students", "userid = '$user->userid' ".
                                      "AND course = '$user->course' AND id <> '$user->id'");
             }
         }