Left 4 Dead 2, Valve’s iconic zombie shooter, turns 11 next month. Today, the game gets a final, massive update — The Last Stand, created by the Left 4 Dead community update team and endorsed by Valve itself. It’s also the first new content added to the game since 2012, according to Polygon. (That was the community-made DLC Cold Stream.)

The update adds tons of new content to the game: new weapons, new maps, new enemy types, unused dialogue, and even a new campaign. The update is free to download, and Left 4 Dead 2 itself is also free to play until September 28th — so there’s no reason not to grab it right now.

And this isn’t the first — or highest-profile — time that Valve has endorsed a fan-made update to one of its games. That honor goes to Black Mesa, a remake of the original Half Life that took 15 years to make and publish. (It just left early access this year, though work on the project began in 2005.)

As Polygon noted, the announcement for this new update was made on the old official Left 4 Dead site.

“It has been many years since the infection first hit. Radio silence, no sign of life, nothing but lingering hopes... CEDA is not going to save us,” the post reads. “But there is hope! A few brave souls have continued the fight against all odds, and soon we can all benefit from their resilience.” That day has come. It’s time to go kill some more zombies.