permission denied for tablespace pg_global?

Hi.

I'm looking at the strange phenomenon....
--
C:\Program Files\PostgreSQL\8.3-beta1\bin>psql postgres postgres
Password for user postgres:
Welcome to psql 8.3beta1, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit

postgres=# select *,oid from pg_catalog.pg_tablespace;
spcname | spcowner | spclocation | spcacl | oid
------------+----------+-------------+--------+------
pg_default | 10 | | | 1663
pg_global | 10 | | | 1664
(2 rows)

postgres=# SELECT pg_size_pretty(pg_tablespace_size(1663));
pg_size_pretty
----------------
13 MB
(1 row)

postgres=# SELECT pg_size_pretty(pg_tablespace_size(1664));
ERROR: permission denied for tablespace pg_global
postgres=#

/END

Have I overlooked the present specification change?
or can someone suggest?

Regards,
Hiroshi Saito