This is a good old case of RTFM, but since I spent a couple of hours figuring it out, I thought I’d blog about it anyway…

The WhiteSpace package in Emacs allows you to visualize whitespace in your code. The overall settings of the package are controlled with the ‘whitespace-style’ variable. Before Emacs 23 you didn’t need to include the ‘face’ option to make different faces work. However, since Emacs 23 you need to have it set.

Now I can keep obsessing about whitespace with an up-to-date version of Emacs, and maybe publicly posting stuff like this will help me remember to RTFM in the future also :)