diff --git a/phpgwapi/inc/class.db_backup.inc.php b/phpgwapi/inc/class.db_backup.inc.php
index 21de95b717..97fcb025c5 100644
--- a/phpgwapi/inc/class.db_backup.inc.php
+++ b/phpgwapi/inc/class.db_backup.inc.php
@@ -330,6 +330,7 @@ class db_backup
 		'httpproxy_server_username',
 		'httpproxy_server_password',
 		'system_charset',
+		'install_id',	// do not restore install_id, as that would give two systems with identical install_id
 	);
 
 	/**