Herald of fire gfx artifact (screenshot)

Hi,

I noticed a while ago that there is a strange graphical artifact
that appears when I cast herald of fire. I got a screenshot too!

http://imgur.com/khNUSs6

I am running windows 7, have nvidia gfx.

using a witch wander with shield.

not an important problem at all, does not appear to cause
any sort of issues for me. just a graphical glitch.

Happens to me too, no idea why. Honestly think it's kinda cool though.