7.0.3: order by func in union

PostgreSQL 7.0.3 on sparc-sun-solaris2.6, compiled by gcc 2.95.2

drop table tryam;
create table tryam (x text);
insert into tryam values ('22');
insert into tryam values ('1');

test=# select x from tryam union select x from tryam;
x
----
22
1
(2 rows)

test=# select x from tryam union select x from tryam order by x;
x
----
1
22
(2 rows)

test=# select x from tryam union select x from tryam order by length(x);
x
----
1
22
1
22
(4 rows)

???

Vadim