COLUMN_GET on a subkey with more than three key value pairs returns a corrupted dyncol_blob

MariaDB> select column_json(column_get(column_create('test1', column_create('key1','value1','key2','value2')) , 'test1' as char));

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

| column_json(column_get(column_create('test1', column_create('key1','value1','key2','value2')) , 'test1' as char)) |

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

| {"key1":"value1","key2":"value2"}                                                                                 |

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

1 row in set (0.00 sec)

MariaDB> select column_json(column_get(column_create('test1', column_create('key1','value1','key2','value2','key3','value3')) , 'test1' as char));

ERROR 1919 (HY000): Encountered illegal format of dynamic column string