diff --git a/calendar/setup/tables_update.inc.php b/calendar/setup/tables_update.inc.php
index f0b0971b4b..e3128a3bc4 100644
--- a/calendar/setup/tables_update.inc.php
+++ b/calendar/setup/tables_update.inc.php
@@ -1992,7 +1992,7 @@ function calendar_upgrade1_8()
 }
 
 /**
- * Convert bool column cal_deleted with egw_api_content_history table to a unix timestamp
+ * Convert bool column cal_deleted to a unix timestamp
  *
  * Using cal_modified as deleted-timestamp, as querying it from SyncML tables creates too many problems (refresh table stops before copying all rows!)
  *
@@ -2000,12 +2000,6 @@ function calendar_upgrade1_8()
  */
 function calendar_upgrade1_9_001()
 {
-	// delete in the past wrongly created entries for a single recurrence, which mess up the update, beside being wrong anyway
-	$GLOBALS['egw_setup']->db->delete('egw_api_content_history',array(
-		'sync_appname' => 'calendar',
-		"sync_contentid LIKE '%:%'",
-	), __LINE__, __FILE__);
-
 	/* done by RefreshTable() anyway
 	$GLOBALS['egw_setup']->oProc->AlterColumn('egw_cal','cal_deleted',array(
 		'type' => 'int',