The 31-year-old champion started poorly in front of hometown fans in Birmingham, Alabama, and was trailing on the scorecards when he sprang to life in the fifth round, knocking Washington down with a right-left combination.
"I said I wasn't going nowhere. I am still here. We are going to keep the fights coming," Wilder said. It was the first fight for Wilder since he broke his right hand and suffered a torn right biceps muscle in an eighth-round stoppage of US veteran Chris Arreola in July. Wilder, who won the title in 2015 with a unanimous 12-round decision over Canadian Bermane Stiverne, improved to 38-0 with 37 knockouts.
Despite being a fill-in opponent for Wilder, Washington gave the champ trouble in the first few rounds.
Copyright Agence France-Presse, 2017