Overidding default values of inherited tables

Please let me know how to overide the DEFAULT value in
inherited tables?
(using PG 7.0.2)

create table objects (
       id serial,
       type name DEFAULT 'object'
       );

create table books (
       title name,
--     type name DEFAULT 'book'  <--- how to do?
       ) inherits(objects);

create table hats (
       color name,
--     type name DEFAULT 'hat'  <--- how to do?
       ) inherits(objects);


PG tells me I cannot redefine the attribute "type",
right, but how about redefining the default value...