Returning to default (e.g. blank) table permissions after a revoke?

If I create a new table the "Access privileges" are blank, which gives
implicit access to the table owner.
But if I touch the grants, then revoke, the privileges are set to {}
which is not the same thing:

production=> create table zzz_junk1 ();

production=> \z zzz_junk1
Schema | Name | Type | Access privileges
--------+-----------+-------+-------------------
public | zzz_junk1 | table |

production=> grant all on zzz_junk1 to production;
production=> \z zzz_junk1
Access privileges for database "production"
Schema | Name | Type | Access privileges
--------+-----------+-------+--------------------------------
public | zzz_junk1 | table | {production=arwdxt/production}

production=> revoke all on zzz_junk1 from production;
production=> \z zzz_junk1
Access privileges for database "production"
Schema | Name | Type | Access privileges
--------+-----------+-------+-------------------
public | zzz_junk1 | table | {}

How can I return to the initial state, where the "Access privileges" are
unspecified?
I'm using Postgres 8.3 here.
http://www.postgresql.org/docs/8.3/static/sql-grant.html does not seem
to cover this topic.