Dots appear in the top left corner of bordered clients

[cmvnd]

Another aesthetic bug: for any client with a border of any size (most commonly for me 1px), an apparently 1x1 dot appears in the top left corner. It appears regardless of the border's color: for example, it shows up as a dark dot (as shown); for a dark border, it appears as a bright dot. However, the dots fail to show up on clients w/o borders. The bug can be recreated by spawning a bordered client (or two), then switching to another tag; upon returning to the tag, the dots will be present. They disappear upon shifting focus to the affected client(s).

This bug apparently doesn't affect some people, but I don't know why.

Examples:
https://goput.it/qs7.png
http://goput.it/tyd.png
http://goput.it/pao.gif (notice Firefox and the top right urxvt)