(London) Oleksandr Usyk has confirmed he is relinquishing his IBF title, just weeks after becoming undisputed heavyweight champion of the world.

The 37-year-old Ukrainian became the first heavyweight to hold the IBF, WBO, WBA and WBC belts when he defeated Tyson Fury by split decision in Saudi Arabia last month.

With Usyk now under contract for a rematch with the Briton scheduled for December 21 in Riyadh, he is unable to defend the IBF crown against interim champion and mandatory challenger Daniel Dubois.

That means Dubois’ fight against fellow Briton Anthony Joshua, scheduled for September at Wembley, could be contested with the vacant IBF title at stake.

Usyk said in a video posted to social media Tuesday: “Anthony and Daniel, listen. I know the IBF title is important to you. This is my gift to you on September 21.”

Briton Lennox Lewis was the last man to unify the main heavyweight belts –– three at the time – before Usyk, in 1999.