filter insertion into DB fails under PostgreSQL

I get the following on the admin/system/filters page consistantly:

user error: DB Error: unknown error
query: INSERT INTO filters (module, weight) VALUES ('image', 0) in /(...)/includes/database.pear.inc on line 89.

More information:

wfire-drupal=# INSERT INTO filters (module, weight) VALUES ('image', 0);
ERROR: Cannot insert a duplicate key into unique index filters_pkey
wfire-drupal=# select * from filters ;
module | weight
--------+--------
filter | 0
(1 row)

Looking at the schema:

CREATE TABLE filters (
module varchar(64) NOT NULL default '',
weight smallint DEFAULT '0' NOT NULL,
PRIMARY KEY (weight)
);

I see that the primary key is "weight", which sure enough means that you can not insert it with a value of 0, since "filters" is already there with that value.

A workaround for this is simply to give the "Legacy Filters (aparently module "filter") a weight other than 0.

For further amusment, if you insert a new filter, such as bbcode, IT ends up with the "0" weight, and you have to again change it so that image can be created.