diff --git a/teacherview.php b/teacherview.php
index d4e7549..8d76aa4 100644
--- a/teacherview.php
+++ b/teacherview.php
@@ -148,7 +148,7 @@ function scheduler_print_schedulebox(scheduler $scheduler, $studentid, $groupid
     $actionurl = new moodle_url($baseurl, array('what' => 'addslot'));
 
     if (!$scheduler->has_available_teachers()) {
-        throw new moodle_exception('needteachers', 'scheduler', viewurl);
+        throw new moodle_exception('needteachers', 'scheduler', $viewurl);
     }
 
     $mform = new scheduler_editslot_form($actionurl, $scheduler, $cm, $groupsicansee);