Bad results near DST change with a dynamic SQL TIMESTAMP parameter

SET time_zone='Europe/Moscow';

CREATE OR REPLACE TABLE t1 (a TIMESTAMP);

SET timestamp=1288477526;  -- this is summer time

INSERT INTO t1 VALUES (NOW());

SET timestamp=1288477526+3600; -- this is winter time

INSERT INTO t1 VALUES (NOW());

SELECT a, UNIX_TIMESTAMP(a) FROM t1;

DELIMITER $$

BEGIN NOT ATOMIC

  DECLARE ts0 TIMESTAMP DEFAULT (SELECT MIN(a) FROM t1);

  DECLARE ts1 TIMESTAMP DEFAULT (SELECT MAX(a) FROM t1);

  SELECT a, UNIX_TIMESTAMP(a) FROM t1 WHERE a=ts0;

  SELECT a, UNIX_TIMESTAMP(a) FROM t1 WHERE a=ts1;

  EXECUTE IMMEDIATE 'SELECT a, UNIX_TIMESTAMP(a) FROM t1 WHERE a=?' USING ts0;

  EXECUTE IMMEDIATE 'SELECT a, UNIX_TIMESTAMP(a) FROM t1 WHERE a=?' USING ts1;

END;

$$

DELIMITER ;

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

| a                   | UNIX_TIMESTAMP(a) |

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

| 2010-10-31 02:25:26 |        1288477526 | <-- correct, this is the minumum value

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

1 row in set (0.001 sec)

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

| a                   | UNIX_TIMESTAMP(a) |

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

| 2010-10-31 02:25:26 |        1288481126 | <-- correct, this is the maximum value

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

1 row in set (0.001 sec)

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

| a                   | UNIX_TIMESTAMP(a) |

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

| 2010-10-31 02:25:26 |        1288477526 | <-- correct, this is the mininum value

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

1 row in set (0.001 sec)

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

| a                   | UNIX_TIMESTAMP(a) |

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

| 2010-10-31 02:25:26 |        1288477526 | <-- wrong, this is NOT the maximum value

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

1 row in set (0.001 sec)