bug in delete rule ?

hello
i have a view which joins two tables
CREATE VIEW ALL_CENTERS AS
SELECT
t0.center_id,
t0.institution,
t0.category,
t0.street_number,
t0.street_name,
t0.postcode,
t0.district_name,
t0.city_name,
t0.province_name,
t0.country,
t1.update_date,
t1.number_of_beds,
t1.chief,
t1.phone_center,
t1.fax_center
FROM
center t0,
center_var t1
WHERE
t0.center_id = t1.center_id;

and i create a rule for deleting using the view:
CREATE RULE ALL_CENTERS_DEL AS ON DELETE TO all_centers
DO INSTEAD (
DELETE FROM center_var WHERE
center_id = OLD.center_id;
DELETE FROM center WHERE
center_id = OLD.center_id;
);

but i this rule delete only line in center_var
and do not remove the line in center table

why ?

sylvain