mod_headers & Server Header Masking

[tekcsound]

Hello, this is my first post on this forum. I'd thought about joining the Apache mailing list, but the last thing I need is yet another high-volume mailing list to sort through! Anyway, on to the question:

I'm trying to change my server header output as per the "instructions" at:
[port80software.com...]

Supposedly, I can change and/or mask the headers like Sun's Java System Web Server does by default (but minus the $1500 price tag!)

I put the:
Header set Server "whatever"
right below:
ServerSignature On
in httpd.conf. Still, when I check the server response, it still lists:
Server: Apache/2.x... etc.

Am I doing something wrong here?