World War Z, the third-person cooperative zombie shooter, took the world by surprise recently, going on to claim more than a million sales in a single week. About 250,000 copies were sold on the Epic Games Store, which developer Saber Interactive is attributing to that storefront’s exclusivity.

I think it’s fair to say most folks went into World War Z with low expectations. The property isn’t exactly a hot item these days and we’ve got plenty of similar zombie shooters to choose from. But based on reviews and fan reaction, Saber managed to put together a pretty solid romp that’s keeping players coming back for more.

As noted in a chat with VentureBeat, Saber chief executive Matthew Karch said the studio was very surprised by the game’s reception, noting that a quarter of its total copies sold were on the PC. While he didn’t offer additional details to support the claim, Karch went on to claim that the team credits its exclusivity deal with the Epic Store for that success.

Maybe Epic is throwing some fantastic support their way or maybe it’s easier for a game like World War Z to stand out on a storefront that doesn’t have a decade’s worth of games on it but, for whatever reason, this is an example of another developer who seems very happy with their decision to side with Team Epic. And since Saber isn’t exactly a massive team and they clearly put in a lot of work to make a solid product, I imagine they’re quite pleased with the fact that they get an even bigger cut of the profits by siding with Epic over Valve’s Steam storefront, too.

We saw a similar story with the latest Metro game, where the developers noted that Exodus sold more than twice as many units on the Epic storefront than the previous game in the series sold on Steam.

It’s an interesting landscape for PC gaming right now, so it’ll be interesting to see if success stories like this encourage additional developers/publisher to do exclusivity deals with Epic. At the moment, it looks like Steam might actually have a fight on its hands.