Converting INET6 to CHAR(39) produces garbage without a warning

CREATE OR REPLACE TABLE t1 (a INET6);

INSERT INTO t1 VALUES ('2001:db8::ff00:42:8329');

SELECT CAST(a AS CHAR(39)) FROM t1;

ALTER TABLE t1 MODIFY a CHAR(39);

SELECT * FROM t1;

MariaDB [test]> SELECT CAST(a AS CHAR(39)) FROM t1;

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

| CAST(a AS CHAR(39))    |

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

| 2001:db8::ff00:42:8329 |

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

1 row in set (0.000 sec)

MariaDB [test]> ALTER TABLE t1 MODIFY a CHAR(39);

Query OK, 1 row affected (0.843 sec)               

Records: 1  Duplicates: 0  Warnings: 0

MariaDB [test]> SELECT * FROM t1;

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

| a                   |

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

¸      ÿ  Bƒ)    |

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

1 row in set (0.001 sec)