numeric fields and null

Im trying to pull out all records in a table where field
'postaladdressid=null' but I cant figure this out.

\d users
....
id | numeric
postaladdressid | numeric
....

adhoc=# update users set postaladdressid=null where id=50;
UPDATE 1

adhoc=# select id,postaladdressid from users where postaladdressid=null;
id | postaladdressid
----+-----------------
(0 rows)

Why did it not select record 50?

just for your info, this is what record 50 looks like.
adhoc=# select id,postaladdressid from users where id=50;
id | postaladdressid
----+-----------------
50 |
(1 row)

Don
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