Unexpected ER_VERS_ENGINE_UNSUPPORTED upon dropping versioning on a partitioned table

MariaDB [test]> CREATE OR REPLACE TABLE t (a INT) WITH SYSTEM VERSIONING PARTITION BY SYSTEM_TIME (PARTITION p1 HISTORY, PARTITION pn CURRENT);

Query OK, 0 rows affected (0.66 sec)

MariaDB [test]> ALTER TABLE t DROP SYSTEM VERSIONING;

ERROR 4109 (HY000): Transaction system versioning for `#sql-69b8_a` is not supported