Server signature apache 2

Hey guys, I'm trying to remove any infos relative to apache, so I added to my httpd.conf in /etc/apache2 these two lines:

ServerSignature Off
ServerTokens Prod

then I restart the server, but infos still show up. So I decided to edit directly apache2.conf at the whole bottom, and added these two lines again, and it worked :o

Do you have an idea of what would cause this? Something in apache2.conf overwriting my rules after it includes the httpd.conf?

thanks for your time!

I'm using ubuntu 10.04 btw!