GRANT role TO PUBLIC- not working?

I'm having problems granting a role to PUBLIC.  According to the manual,
you do this by:
    GRANT role TO PUBLIC;

but when I try this, I get an error:

bhurt_dev=# GRANT test_role TO PUBLIC;
ERROR:  role "public" does not exist
bhurt_dev=#

This is Postgresql 8.01.0004.  Any ideas?

Brian