problem selecting rows with null value

I am sure that I am doing something subtly wrong with my sql syntax
here. I thought that it was a timestamp null column issue, but it
doesn't work with int either. Is there a special way to denote the null
value in a situation like this that I don't know about?

tsc=# create table pleah(
tsc(# foo INT NOT NULL,
tsc(# bar timestamp DEFAULT NULL );
CREATE TABLE
tsc=# insert into pleah (foo) values (1);
INSERT 206475246 1

###ok here I would just like to select that row that I just inserted...
but no!

tsc=# select * from pleah where bar = NULL;
foo | bar
-----+-----
(0 rows)

tsc=# select * from pleah;
foo | bar
-----+-----
1 |
(1 row)

thanks muchly
matthew