SQL-Query error with PGSQL 6.5beta1

Hi!

If there is a separate beta mailing list for these kind of incidents, I
am sorry, but I could not find it.

Now, here is the problem. The following query fails with PGSQL 6.5beta1,
even though it seems correct:

select superext as name from OM_ExtendInheritance where subext in (
select superext as name from OM_ExtendInheritance where subext in (
select 'Patient' as name
)
union select 'Patient' as name
);

Postgresql reports:
ERROR: parser: parse error at or near "union"

Could there be a problem handling nested expressions?

Thank you!

Regards
Joerg Fischer