Using MATCH returns NULL for Virtual Column

CREATE TABLE `simple_virtual_column` (

  `a` varchar(255) DEFAULT NULL,

  `b` varchar(255) GENERATED ALWAYS AS (`a`) VIRTUAL,

  FULLTEXT KEY `a` (`a`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO simple_virtual_column (a) VALUES ('test');

SELECT * FROM simple_virtual_column WHERE MATCH(a) AGAINST('test');

| test | NULL |

SELECT * FROM simple_virtual_column;

|test | test |