A knee injury has forced Alexander Gustafsson to pull out of his rematch against Jon Jones at UFC 178 and replacing Gustafsson in the bout will be Daniel Cormier. 
The fight change was announced by UFC President Dana White on Wednesday.
UFC 178 will come from the MGM Grand Garden Arena in Las Vegas on September 27th and tickets for the event go on sale next week.
Cormier (15-0) has won both of his fights since dropping down to the light heavyweight division and is coming off a win against Dan Henderson at UFC 173 in May. He was scheduled to have knee surgery recently, but he decided to delay the surgery.
Jones (20-1) will be fighting in Las Vegas for the first time since 2011 and this will be his first title defense in the fight capital of the world. His most recent title defense came in April as he defeated Glover Teixeira by unanimous decision.
The current UFC 178: Jones vs. Cormier fight card is below.
Jon Jones (20-1) vs. Daniel Cormier (15-0)
Tim Kennedy (18-4) vs. Yoel Romero (8-1)
Dominick Cruz (19-1) vs. Takeya Mizugaki (20-7-2)
Cat Zingano (8-0) vs. Amanda Nunes (9-3)
Brian Ebersole (50-16, 1NC) vs. John Howard (22-9)
Patrick Cote (20-8) vs. Stephen Thompson (9-1)
Conor McGregor (15-2) vs. Dustin Poirier (16-3)