(Photo : Kevin Winter/Getty Images for iHeartRadio / ANDRE DIAS NOBRE/AFP via Getty Images) Green Day’s Billie Joe Armstrong and Taylor Swift.File this under things you wouldn’t expect. Green Day frontman Billie Joe Armstrong is a Taylor Swift fan and took to Instagram on Monday (June 3) to rave about her show in Lyon, France.

“Just saw Taylor Swift eras tour in Lyon, France!! Great production. Great voice. Great entertainer. Great songwriting. Crazy crowd,” he wrote alongside a photo of himself, showing off some of the new gear he picked up at the show.

“People even shared with me some friendship bracelets. Thanks a million @taylorswift. My bracelets say #sexybaby #assholeoutlaw,” he added.

Armstrong isn’t the only famed music personality that you wouldn’t necessarily peg as a Swift fan. Flavor Flav, the hype man of hip-hop act Public Enemy, also came out as a Swiftie and has attended multiple shows.

Armstrong’s post got some interesting fan reactions, including at least one response from a famous friend. “Without me???” posted tennis star Serena Williams.

Other less famous fans also had some interesting comments. “MY TWO FAVORITE ARTISTS IN THE SAME PLACE OMG,” wrote one fan. Another added, “Billy Swiftie. This is punk love.”

While Swift continues her world dominating Eras Tour in Europe, Green Day is also on tour on the continent, playing France on Wednesday (June 5) at the LDLC Arena on The Saviors Tour. The band has dates in Europe through the end of June, wrapping up June 29 at Wembley Stadium in London.

Green Day kicks off their U.S. dates July 29 at National Park in Washington, D.C. with opening acts the Smashing Pumpkins, Rancid and the Linda Lindas. The band’s U.S. dates wrap Sept. 28 at Petco Park in San Diego.

Swift, meanwhile, next plays Edinburgh, Scotland on Friday (June 7) with opening act Paramore. She wraps her European dates at Wembley Stadium in London on Aug. 20 and restarts the Eras Tour in Toronto on Nov. 14 with new opening act Gracie Abrams.