INSERT .. PARTITION (partition_list) (column_list) VALUES ... syntax stopped working

INSERT 

 INTO tbl_name PARTITION (partition_list) (col,...)

VALUES (expr,...),(...)

MariaDB [test]> insert into tp partition (p1) (a) values (1);

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'a) values (1)' at line 1

MariaDB [test]> select @@version;

+----------------------+

| @@version            |

+----------------------+

| 10.4.1-MariaDB-debug |

+----------------------+

1 row in set (0.00 sec)

MariaDB [test]> insert into tp partition (p1) (a) values (1);

Query OK, 1 row affected (0.04 sec)

MariaDB [test]> select @@version;

+-----------------------+

| @@version             |

+-----------------------+

| 10.3.12-MariaDB-debug |

+-----------------------+

1 row in set (0.00 sec)