Louis Tomlinson and Bebe Rexha Added to iHeartRadio Music Festival Lineup

Louis Tomlinson Bebe Rexha Performance
Kevin Winter/Getty Images

There's been a last-minute add to this weekend's iHeartRadio Music Festival.

Louis Tomlinson and Bebe Rexha will be taking the stage at the Ryan Seacrest-hosted event -- which takes place on Sept. 22 and 23 at Las Vegas' T-Mobile Arena to perform their collaboration, "Back to You."

The pair joins previously announced acts, Coldplay, The Weeknd, Lorde, Kings of Leon, Pink, Miley Cyrus and Big Sean, as well as performances by Harry Styles, Chris Stapleton, Thirty Seconds to Mars, Niall Horan, DJ Khaled, David Guetta, Thomas Rhett and Kesha.

Tickets are on sale at AXS.com.

Meanwhile, Rexha and Grace VanderWaal totally fangirled over each other at this year's Teen Choice Awards.

Watch the video below for the awesome moment.