Updating a table via a view

I am trying to maintain a history of rows. The base table has a start
and end date. I am updating the table using a view and a rule. The
rule, updates the end date on the current record and then inserts a new
row with the modified columns, or at least thats what I want to happen.

The update is occuring but the insert doesn't. I get no error but no
row. The rule looks like this;

CREATE RULE a_update
AS ON UPDATE TO a DO INSTEAD
(UPDATE a_hist
SET tend = now()
WHERE (a.x = old.x)
AND (a.tend = 'infinity'::timestamptz);
INSERT INTO a_hist (
x,
tstart,
tend,
y,
z
) VALUES (
new.x,
now(),
'infinity'::timestamptz,
new.y,
new.z
);
);

Any pointer as to what I am doing wrong ?

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