Primary key inheritance problem

Hello,

I've a strange problem with inheritance on PostgreSQL 7.4.1. It seems
like tables don't inherits the primary key of the 'mother' table.
Here's a little sample to show my problem :

CREATE TABLE foo_a
(
pk_idmyfoo INT2 PRIMARY KEY NOT NULL,
myfoo_name VARCHAR(10)
);

CREATE TABLE child_foo
(
child_foo_nickname VARCHAR(20)
) INHERITS (foo_a);

CREATE TABLE childfoo_bookmarks
(
fk_idchildfoo INT2 NOT NULL REFERENCES child_foo (pk_idmyfoo),
url VARCHAR(250)
);

The error I get is :
ERROR: there is no unique constraint matching given keys for referenced
table "child_foo"

What can I do to solve that problem ?

Thanks in advance for your help !

--
Bruno Baguette - pgsql-ml(at)baguette(dot)net