diff --git a/admin/cron.php b/admin/cron.php
index fe9157a842330..20c138a178180 100644
--- a/admin/cron.php
+++ b/admin/cron.php
@@ -43,9 +43,10 @@
 
     if ($CFG->longtimenosee) { // value in days
         $cutofftime = time() - ($CFG->longtimenosee * 3600 * 24);
-        if ($users = get_records_sql("SELECT * FROM user 
+        if ($users = get_records_sql("SELECT u.* FROM user u, user_students s
                                        WHERE lastaccess > '0' AND 
-                                             lastaccess < '$cutofftime'")) {
+                                             lastaccess < '$cutofftime'
+                                             u.id = s.user GROUP BY u.id")) {
             foreach ($users as $user) {
                 if (delete_records("user_students", "user", $user->id)) {
                     echo "Deleted student enrolment for $user->firstname $user->lastname ($user->id)\n";