diff --git a/main/calendar/agenda.lib.php b/main/calendar/agenda.lib.php
index 529e296e6a..dd5a7155d3 100755
--- a/main/calendar/agenda.lib.php
+++ b/main/calendar/agenda.lib.php
@@ -1428,7 +1428,7 @@ class Agenda
                 $user_to_array = $items['users'];
                 $event = array();
                 $event['id'] = 'course_'.$row['id'];
-                $event['unique_id']  = 'course_'.$row['id'].intval($row['session_id']);
+                $event['unique_id']  = 'event_'.$row['id'].'_'.intval($row['session_id']).'_'.$course_id;
 
                 // To avoid doubles
                 if (in_array($event['unique_id'], $eventsAdded)) {