Karlie Kloss and Christian Siriano have joined Bravo's Season 17 of Project Runway as host and mentor.

Kloss and Siriano will replace former stars Heidi Klum and Tim Gunn who exited Project Runway in September to appear on a new fashion reality series for Amazon.

The duo will be joined by fashion designer Brandon Maxwell and former Teen Vogue editor-in-chief Elaine Welteroth as judges in place of Zac Posen. Nina Garcia is set to return as a judge.

The new cast was announced by Kloss on Twitter Wednesday alongside promotional photos for Season 17. "Get ready for the boldest collection yet," she said.

Project Runway Season 17 is set to premiere in 2019. Klum and Gunn had previously starred on all 16 seasons of Project Runway which returned to Bravo in May. The series had moved to Lifetime in 2008 after airing for five seasons on Bravo.

"As someone who grew up watching Project Runway, I could not be more excited to host and produce a series that provides a platform to aspiring American designers as they pursue their creative and entrepreneurial dreams," Kloss said in a statement.

"I am equally as thrilled to work alongside an incredibly talented group of fashion innovators - Brandon Maxwell, Elaine Welteroth, Nina Garcia and Christian Siriano - to inspire, support and help guide these designers as they realize their visions and build everlasting brands and businesses," she continued.

"Project Runway has offered such wonderful opportunities for so many and I'm excited to take on this role as a mentor. I hope to guide and inspire the new talent on the rise," Siriano said.