diff --git a/calendar/inc/class.calendar_datasource.inc.php b/calendar/inc/class.calendar_datasource.inc.php
index 16970ff2b9..eb1bafc479 100644
--- a/calendar/inc/class.calendar_datasource.inc.php
+++ b/calendar/inc/class.calendar_datasource.inc.php
@@ -10,6 +10,7 @@
  * @version $Id$
  */
 
+use EGroupware\Api;
 use EGroupware\Api\Link;
 use EGroupware\Api\Acl;