Redirect problem

Hi!

I read somewhere that this would redirect all request for non-existent
pages/directories to mypage.php:

Options +FollowSymLinks
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule . /mypage.php

The problem is it redirect everything, also requests for existing pages and
directories. I want to be able to access existing content directly. Please
advice!

Thank you!

markus