Update tsvector trigger

Hi,

i´m trying to do a trigger that its called when update or insert, that
update the tsvectors, for text-search. Here´s my code:

create table x(
cod serial,
texto text,
vectors tsvector,
constraint pk primary key(cod)
);

CREATE OR REPLACE FUNCTION atualiza_vectors() RETURNS trigger AS $$
BEGIN
IF NEW.texto<>NULL THEN
UPDATE x SET vectors = to_tsvector(lower(to_ascii(NEW.texto)))
where cod= NEW.cod;
END IF;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER atualiza_vectors AFTER INSERT OR UPDATE ON x
FOR EACH ROW EXECUTE PROCEDURE atualiza_vectors();

When the trigger its called, postgre shows the following error: "stack depth
limit exceeded".

Did anyone knows what its wrong?