Insert NULL date field - Mailing list pgsql-general

I have a table in postgresql 6.4.2 that has date fields. I'm trying to
insert a null into the date field and cannot find any docs on how to do
this. Can someone please give me some help.

insert into employee ( empnumber, hiredate, terminationdate ) values (
4, '04/19/99', NULL )

the above NULL does not seem to work.

Thanks in advance