Earlier this summer, Dave Grohl told Rolling Stone that “the biggest pop star in the world” would guest on Concrete And Gold, the new album from his Foo Fighters. He wouldn’t say who the pop star was; he’d only drop vague hints. When Grohl made those claims, I was convinced that the mystery guest in question was Lady Gaga. I was wrong. Grohl has now revealed who the guest is, and it’s Justin Timberlake.

Grohl spilled the beans in yet another recent Rolling Stone interview. Speaking with the magazine’s Josh Eells, Grohl said how the collaboration came to be:

[Timberlake] listened to what the Foos were doing and liked what he heard, and pretty soon he and Grohl were hanging out regularly. “We’d drink whiskey in the parking lot,” Grohl says. “He was really, really cool. Then the night before his last day, he says, ‘Can I sing on your record? I don’t want to push it, but – I just want to be able to tell my friends.’?” So the band had him add some “la la la’s” to one track. “He nailed it,” Grohl says. “I’m telling you – the guy’s going somewhere.”

Concrete And Gold also features Paul McCartney and Boyz II Men’s Shawn Stockman. It’s out 9/15 on Roswell/RCA.