Kalista W Bug

So I just got through playing a game as Thresh, with my friend playing Kalista. He bound to me at the beginning of the game, as per usual, and we headed into lane. We soon noticed that Kalista's W had the wrong effect. Whenever anything died from the W damage, me (Thresh) got the gold and cs from it. We did this with me placing the mark and Kalista proccing it, and with Kalista placing the mark and me proccing in. It was the same result. Please fix.