SPATIAL index fails to work with CONTAINS

create table gisbug(id int not null primary key, g1 geometry not null, spatial index(g1));

insert into gisbug values(1, polygonfromtext('POLYGON((0 0, 0 5, 5 5, 5 0, 0 0))'));

explain select id from gisbug where contains(g1, pointfromtext('POINT(1 1)'));

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

| id   | select_type | table  | type  | possible_keys | key  | key_len | ref  | rows | Extra       |

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

|    1 | SIMPLE      | gisbug | range | g1            | g1   | 34      | NULL |    1 | Using where |

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

select id from gisbug where contains(g1, pointfromtext('POINT(1 1)'));

Empty set (0.01 sec)

alter table gisbug drop index g1;

select id from gisbug where contains(g1, pointfromtext('POINT(1 1)'));

+----+

| id |

+----+

|  1 |

+----+