BUG #13769: SELECT ... FROM a JOIN b FOR UPDATE a; BREAKS SNAPSHOT

The following bug has been logged on the website:

Bug reference: 13769
Logged by: Konstantin Evteev
Email address: konst583(at)mail(dot)ru
PostgreSQL version: 9.2.13
Operating system: Debian GNU/Linux 7.9 (wheezy)
Description:

Select of 2-nd transaction will return new value from a and old value from
b

CREATE TABLE a
(
id integer,
val1 integer
);

CREATE TABLE b
(
id integer,
val1 integer
);

insert into a select 1,2;
insert into b select 1,3;

--FIRST TRANSACTION
begin

select * from a inner join b
on
a.id = b.id
where
a.id =1 for update of a;

update a set val1 = 0 where id = 1;
update b set val1 =0 where id = 1;

end

-- SECOND TRANSACTION (starts during executing of first transaction)
select * from a
inner join
b on a.id = b.id
where a.id =1 for update of a

--result:
1;0;1;3