Having trouble with pg_dumpall -o

Hi PostgreSQL users,

I'm having difficulty migrating a postgres 8.4.11 database to postgres
9.1.2, neither of the included pg_dumpall tools appear to honour the -o or
--oids options and fail to dump the table oids from the old database as we
require.

I've tried various combinations and orders of options including those
below:-
pg_dumpall -o -p 5432 -U postgres > dump_o.sql
pg_dumpall --oids -p 5432 -U postgres > dump_o.sql
pg_dumpall -p 5432 -U postgres -o > dump_o.sql
pg_dumpall -p 5432 -U postgres --oids > dump_o.sql

I'm beginning to think it could just be a bug but I'm not familiar with this
tool and wanted to run it by the community before jumping to conclusions.

Any help is appreciated!

Thanks in advanced,
Matt