Problem with function returning a result set

Hi,

I'm playing around with functions returning result sets, and I have a problem with the following function:

-- Create sample data
CREATE TABLE employee (id integer, first_name varchar(50), last_name varchar(50));
INSERT INTO employee values (1, 'Arthur', 'Dent');
INSERT INTO employee values (2, 'Zaphod', 'Beeblebrox');
INSERT INTO employee values (3, 'Ford', 'Prefect');
COMMIT;

-- Create the function
CREATE OR REPLACE FUNCTION get_employees(name_pattern varchar)
RETURNS TABLE(id integer, full_name text)
AS
$$
BEGIN

RETURN QUERY
SELECT id, first_name||' '||last_name
FROM employee
WHERE last_name LIKE name_pattern ||'%';
END
$$
LANGUAGE plpgsql;

COMMIT;

Now when I run:

SELECT *
FROM get_employees('D');

I get one row returned which is correct, but the ID column is null (but should be 1). It does not depend which row(s) I select through the procedure. I also tried to change the datatype of the returned id to int8 and an explicit cast in the SELECT statement, but to no avail.

When I define the function using SQL as a language (with the approriate changes), the ID column is returned correctly.

I'm using Postgres 8.4.3 on Windows XP
postgres=> select version();
version
-------------------------------------------------------------
PostgreSQL 8.4.3, compiled by Visual C++ build 1400, 32-bit
(1 row)

What am I missing?

Regards
Thomas