Face doesn't need to be your own to trigger achievement

I got the "To Thine Own Self Be True" achievement, which should be triggered by wearing your own face on your face, by wearing a madpole face. However, I am, in fact, not a madpole. Might be because I got the face by dominating the madpole and making it dismember itself, but I was in my own body when I equipped it. I can't really test that anymore.