It looks like Sony’s Days of Play sale is having a positive impact on its PlayStation VR (PSVR) headset.

PlayStation VR Worlds, the PSVR launch title from Sony’s London Studio, ranked in fifth place in this week’s UK games software charts from GFK. That means in the space of this week it even managed to outsell titans like Gran Theft Auto V, Mario Kart 8, Assassin’s Creed Origins and Call of Duty: WWII. The game costs only around £10 during Sony’s current promotion, which ends later this week.

There might be a big reason the game has sold so well, though. Copies of PSVR Worlds are bundled inside pretty much every PSVR unit sold in the UK right now, which will have boosted its sales somewhat. That might seem like cheating, though it actually suggests PSVR itself might have moved a healthy number of units over the course of the promotion. The headset’s starter pack also costs about £200 during the event.

Last we heard, PSVR had sold two million units worldwide. That said, we didn’t get an update on sales at E3 last week, which might suggest Sony hasn’t managed to pass the three million mark just yet.