Limit doesn't work with select unions

I'm doing the following query:
select a.id, cfs.id from cfs where a.id = cfs.oid union select b.id, cfs.id
from cfs where b.id = cfs.oid limit 1;
The limit basically doesn't work. I get the maximum amount of rows back.
I try the query
select a.id, cfs.id from cfs where a.id = cfs.oid limit 1 union select b.id,
cfs.id from cfs where b.id = cfs.oid limit 1;
and psql says the syntax is incorrect. Any ideas on how to use limit with
union queries?
Thanks,
Rich