Hardcore gamers don’t fully trust Facebook and they are dismissive of “Facebook games.” When they see the social network in their “real” games, they worry it will hijack their walls and send invites to their friends. But despite that, one of the biggest developers in the world was able to incorporate Facebook into its game without angering its demanding and fickle community.

Developer Riot has incorporated Facebook into League of Legends, and the players of that game have found little to complain about. This Facebook Login feature connects a player’s account on Riot’s megapopular multiplayer online arena battler (MOBA) with their Facebook social profile. But instead of sending invites and posting wall messages, this is all about helping people find their friends who also play League of Legends. Facebook confirmed to GamesBeat that 4 million players have used this functionality to make 15 million friend connections. That’s a significant chunk of the around 70 million people who actively play League every month. The company thinks this is evidence that it is still an important tool for keeping people — and especially gamers — connected around the world. And this also suggests that developers can hand off the hassle of getting new players to sign up to Facebook without having to worry about a backlash from fans.

“It all starts with the basic idea of creating better gameplay experiences for players,” Facebook director of global games partnerships Leo Olebe told GamesBeat. “At the heart of it, that’s what Riot is always trying to do. Riot reached out and asked how it can help its players find more friends. So the developer started talking to its fans to see if this was something that they really wanted.”

This led Riot to specifically asking for feedback from League players about their concerns with Facebook integration. The studio found that, in general, most people didn’t trust the idea of the social network getting its fingers into League of Legends. Their biggest worry was, of course, that they wouldn’t have control over how Facebook and Riot would post to their profile.

To address such concerns, Riot focused on two key things. It emphasized that this is a “Find your Friends” feature, and it promised never to post to players’ walls. Now that doesn’t mean it will ask for permission before posting — it means it will never post to walls period.

“It was risky to pursue a social feature that had such skepticism among the League community,” League of Legends product manager Matthew Enthoven said. “But by putting players first and really understanding their concerns, we were able to deliver a useful feature that continues to foster meaningful player experiences.”

For Riot, this is a clear benefit. It can keep its players connected with one another and potentially playing more often and for longer periods of time because they are online with their real friends. League of Legends is free-to-play, and it makes around $1 billion per year in revenue from microtransactions. Keeping players coming back over and over and keeping them talking to their friends about the game is crucial. In a game that thrives on those relationships, having 4 million people find 15 million friends that also play League can translate into a huge boost in engagement and revenue.

For Facebook, this is proof that developers can integrate social features from the site without alienating players. The League of Legends community is often loud and obnoxious if it sees Riot doing something it doesn’t approve of. But if they can accept Facebook Login, then it’s likely that any game’s player base will come around to it as well as long as the developer knows what it’s doing.

“You have to talk to the gamers,” said Olebe. “That way you can get ahead of it and reassure people that you’re not going to be posting to their wall and that you’re not going to take over their profiles in a way they don’t want. But yes, you are going to be providing functionality that they’re most interested in.”