weird result with myisam, group_concat and bit column

A colleague noted weird results for a certain SELECT involving

• a bit() column
• an unrelated int ID column
• group_concat on the ID column with additional value being the bit
• and myISAM

Test case:

create database if not exists kicker;

use kicker;

drop table if exists test;

create table test (

	id int(10) unsigned not null,

	val bit(1) not null,

	primary key (id)

) ENGINE=MyISAM;

insert into test set id = 1, val = 0;

insert into test set id = 2, val = 1;

select * from test;

select id, val FROM kicker.test group by id;

select GROUP_CONCAT(id), not not val FROM kicker.test group by id;

SELECT GROUP_CONCAT(id), val FROM kicker.test GROUP BY id;

SELECT GROUP_CONCAT(id, val), val FROM kicker.test GROUP BY id;

The first three selects are OKAY. The last two... show val as bit value 1 for in BOTH result rows.

The last select even shows the correct bit values 0 and 1 respectively in the GROUP_CONCATted colum, but again both rows have val as bit value 1.

The results are correct when I replace ENGINE=MyISAM with InnoDB.

This happens on mariadb 5.5.28 and 10.0.22, both as packaged by openSUSE (11.4 and tumbleweed, respectively)