While Windows 10 has been most Steam users’ OS of choice for quite some time, the last few months have seen Windows 7 slowly gaining ground on the leader. Despite this trend, October’s Steam hardware and software survey data brought some very surprising news: the two operating systems suddenly swapped positions after Windows 7 users increased 22.45 percent while Windows 10 fell by just over 18 percent.

Worldwide, Windows 7 remains the most popular version of Microsoft’s OS, but that’s primarily due to its huge number of enterprise users. The opposite had been true of Steam gamers; so, why the sudden change? It turns out that it's mostly down to one game: PlayerUnknown’s Battlegrounds. Or more specifically, it’s a result of the Battle Royale title's popularity in China and the number of people who use Windows 7 in the country.

The language stats in Steam’s survey back up the theory. They show that the number of people using simplified Chinese increased 27 percent to 56.37 percent last month. During the same period, English dropped 13.4 percent to 21.24 percent.

Despite the privacy enhancements introduced by Microsoft since its release, some people still eye Windows 10 with suspicion when it comes to spying on users. In China, the OS is banned from government systems—Microsoft launched a customized version for authorities earlier this year—and many Chinese consumers prefer to remain on Windows 7.

Battlegrounds has sold around 13 million copies worldwide, so it’s no surprise to see it exert such an influence on the Steam survey. And while it may be extremely popular in China, that didn’t stop many players from the country review bombing the title last month; a result of the in-game ads that had been introduced.

Windows 10 could eventually retake the top position on the Steam survey, though, especially if China carries out its threat to ban Battlegrounds because of the excessive violence and a design that “goes against Chinese values and ethical norms.”