pg_dump serial UNIQUE NOT NULL PRIMARY KEY

Hello, I'm a fairly new user of PostgreSQL 8.0.2 and I'm creating a table like 
this:

CREATE TABLE cases (
     id serial PRIMARY KEY,

Works fine, but when I pg_dump the database, what shows up in the dump is:

CREATE TABLE cases (
     id serial NOT NULL,

The documentation seems to say that 'serial NOT NULL' is not at all the same 
as 'serial PRIMARY KEY':

( http://www.postgresql.org/docs/8.0/static/datatype.html#DATATYPE-SERIAL )

"Note:  Prior to PostgreSQL 7.3, serial implied UNIQUE. This is no longer 
automatic. If you wish a serial column to be in a unique constraint or a 
primary key, it must now be specified, same as with any other data type."

Any help appreciated,
Michael Hipp