Deadlock on the same select for update

Hi,
I have problem with deadlocks and don't know why it happens. Below is
the log (postgres 9.0, debian):

[11882]DETAIL: Process 11882 waits for ShareLock on transaction
44324308; blocked by process 11884.
Process 11884 waits for ShareLock on transaction 44324307;
blocked by process 11882.

Process 11882: SELECT * FROM teddy WHERE id IN
(112747007,112747008,112747011,112747013,112747015,112747016,112747020,112747021,112747022,112747024,112747025,112747028,112747030,112747032,112747034,112747035,112747038,112747043,112747044,112747045,112747050,112747052,112747053)
FOR UPDATE

Process 11884: SELECT * FROM teddy WHERE id IN
(112747007,112747008,112747011,112747013,112747015,112747016,112747020,112747021,112747022,112747024,112747025,112747028,112747030,112747032,112747034,112747035,112747038,112747043,112747044,112747045,112747050,112747052,112747053)
FOR UPDATE

Regards,
Roman