Novak Djokovic beat Jannik Skinner in straight sets Friday morning to reach the Wimbledon final, but it wasn’t without a bit of controversy.

Leading 2-1 during the second set, the 23-time Grand Slam title winner was called for hindrance by umpire Richard Haigh after he let out a long grunt just as Skinner went to return the ball, putting him down 30-15 in the game. 

Djokovic dropped to his knees in disbelief before asking Haigh, “What are you doing?”

Tennis players earn a point for hindrance if the umpire deems the act in question to be on purpose, according to ITF rules. 

If the umpire deems the act to be unintentional, the point is replayed. 

Haigh, apparently, believed it to be the former. 

The 36-year-old tennis legend would win the set 6-4 and, eventually, the match to move onto his ninth Wimbledon final, but the questionable call could have cost him. 

“The hindrance earlier on today in the match could have changed the course of the match. I felt really nervous after that call from the chair umpire but [I] kind of managed through to regroup,” Djokovic said.

“It was, I think, probably the first time in my career that something like this happened. It never happened to me, I don’t normally have extended grunts. Maybe it was an echo from the roof or something like this. You know, I actually didn’t feel I was causing any hindrance to my opponent but it was the kind of call that I have to respect.”

The hindrance call shocked even BBC broadcaster Todd Woodbridge.

“I feel like Richard’s been waiting to make that call for a while,” Woodbridge said. “I’m not sure that it’s worth him interjecting into the match like he has just done. I think that maybe could have been a word to Novak at the changeover to just be aware before giving that. That’s rough.”

John McEnroe, a former world No. 1 and seven-time major winner, said it was a “horrible, horrible call” during the ESPN broadcast, according to the Daily Mirror.

“[Djokovic] handled it admirably,” McEnroe continued, per the Mirror. “Way, way better than most players. I would’ve hated it if that had been the turning point. It’s one thing if Sinner lifts his game – that’s great, competition – but not when the umpire gets in the middle of it.”

Djokovic, who was later called for a questionable delay on a serve, will face Carlos Alcaraz in the Wimbledon final on Sunday. 

The 20-year-old Spaniard took over the World No. 1 spot from Djokovic last month with his win at the Queen’s Club Championships. 

Djokovic, though, got the best of Alcaraz in their last matchup during the semifinals of the French Open.

Djokovic is halfway to a calendar year Grand Slam after wins at the Australian and French Open.