Cannot create a type in pg_catalog

Should this work, or at least give a more appropriate error message?

demo=# SELECT version();
                                         version

------------------------------------------------------------------------------------------
 PostgreSQL 8.2.4 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC)
3.4.2 (mingw-special)
(1 row)

demo=# SELECT rolname, rolsuper, rolcatupdate FROM pg_authid;
 rolname  | rolsuper | rolcatupdate
----------+----------+--------------
 postgres | t        | t
(1 row)

demo=# CREATE TYPE pg_catalog.mytype AS (data text);
ERROR:  permission denied to create "pg_catalog.mytype"
DETAIL:  System catalog modifications are currently disallowed.

I can successfully create functions in pg_catalog, just not types or
relations.

Regards, Dave.