apache2: bad user name ${APACHE_RUN_USER}

While trying to check the vhost configuration on my Kubuntu dev box, I had to run httpd -S. Of course, since ubuntu renamed httpd to apache (a bit like calling a Veyron a Bugatti), I had to run apache2 -S. This however led to the following error message:
apache2: bad user name ${APACHE_RUN_USER}

Looked like a permission issue. A little noodling later I found that the solution is to always use apache2ctl for everything as it is run as the proper user. So it's not httpd. It's not apache. It's not apache2. It's apache2ctl. FFS.

Hope this helps somebody out there :)