can't drop table for SYSTEM VERSIONING

CREATE TABLE `t4` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(100) DEFAULT NULL,

  `ts` timestamp(6) GENERATED ALWAYS AS ROW START,

  `te` timestamp(6) GENERATED ALWAYS AS ROW END,

  PRIMARY KEY (`id`,`te`),

  PERIOD FOR SYSTEM_TIME (`ts`, `te`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 WITH SYSTEM VERSIONING

mysql> set system_versioning_alter_history = 'KEEP';

Query OK, 0 rows affected (0.00 sec)

mysql> alter table t4 DROP PERIOD FOR SYSTEM_TIME;

ERROR 4125 (HY000): Wrong parameters for `t4`: missing 'DROP COLUMN `ts`, DROP COLUMN `te`'

mysql> 

mysql> ALTER TABLE t4 DROP SYSTEM VERSIONING;

ERROR 4125 (HY000): Wrong parameters for `t4`: missing 'DROP COLUMN `ts`'

mysql>