diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 78865a8eb53..f9d120a9a7f 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -596,7 +596,9 @@ function isstudent($courseid, $userid=0) {
         if (isguest($userid)) {
             return false;
         }
-        return record_exists('user_students', 'userid', $userid);
+        return (record_exists('user_students', 'userid', $userid)
+                  or (record_exists('user_teachers', 'userid', $userid)
+                       and !record_exists('user_teachers', 'userid', $userid, 'course', SITEID)));
     }  
 
     if (!$userid) {