diff --git a/calendar/inc/class.calendar_so.inc.php b/calendar/inc/class.calendar_so.inc.php
index a6a51d9cc4..410fb29d2a 100644
--- a/calendar/inc/class.calendar_so.inc.php
+++ b/calendar/inc/class.calendar_so.inc.php
@@ -1536,10 +1536,12 @@ ORDER BY cal_user_type, cal_usre_id
 				$this->db->delete($table, array('cal_id'=>$row['cal_id']), __LINE__, __FILE__, 'calendar');
 			}
 			// handle sync
-			$this->db->query('UPDATE egw_api_content_history
-				SET sync_deleted=NOW()
-				WHERE sync_appname = \'calendar\'
-					AND sync_contentid ='.$row['cal_id'], __LINE__, __FILE__);
+			$this->db->update('egw_api_content_history',array(
+				'sync_deleted' => time(),
+			),array(
+				'sync_appname' => 'calendar',
+				'sync_contentid' => $row['cal_id'],	// sync_contentid is varchar(60)!
+			), __LINE__, __FILE__);
 			// handle links
 			egw_link::unlink('', 'calendar', $row['cal_id']);
 		}