diff --git a/calendar/inc/class.calendar_groupdav.inc.php b/calendar/inc/class.calendar_groupdav.inc.php
index 3b54e91539..7ec451659c 100644
--- a/calendar/inc/class.calendar_groupdav.inc.php
+++ b/calendar/inc/class.calendar_groupdav.inc.php
@@ -660,7 +660,7 @@ class calendar_groupdav extends groupdav_handler
 			}
 		}
 		// if recurring event starts in future behind horizont, nothing will be returned by bo::search()
-		if (!isset($master) && !($master = $this->bo->read($uid)))
+		if (!isset($master) && !($master = $bo->read($uid)))
 		{
 			return array();
 		}