Game, set, boycott.

Tennis umpires are reportedly thinking about unionizing after Serena Williams accused chair umpire Carlos Ramos of sexism in last weekend’s controversial US Open women’s final. What’s more, some are also talking about boycotting the 23-time Grand Slam champion’s future matches.

The tennis officials are allegedly outraged that the International Tennis Federation took nearly 48 hours to come to Ramos’ defense on Monday afternoon, after both the Women’s Tennis Association and the United States Tennis Association supported Williams’ claims that Ramos was holding her to a different standard because she’s a woman. The firestorm ensued last Saturday after Ramos charged Williams with illegal coaching and racket abuse, and then gave her another violation for verbal abuse after the tennis superstar called him a “thief” and a “liar” during the championship match against Naomi Osaka.

This got so much attention in part because so many more people tuned into the women’s final match over the men’s. Fifty percent more people — an average of 3.1 million viewers — watched Williams’ controversial loss to 20-year-old Osaka on Saturday compared to the men’s singles final the next day, which drew in 2.07 million viewers. In fact, the audience for the entire U.S. Open was up 9% from last year with an average of 1.04 million viewers.

And umps aren’t happy about how Ramos got served in the court of public opinion. “There is a lot of unhappiness in the umpiring community because no one is standing up for officials,” an anonymous senior umpire told the Guardian. “Umpires keep asking: ‘What if it was me in that chair on Saturday?’ There is a widespread feeling that Carlos was hung out to dry for nearly 48 hours and that no one is standing up for officials.”

Williams, who won $1.85 million as the runner-up to Osaka, was fined $17,000 Sunday by the tournament’s referee’s office for her violations. The International Tennis Federation confirmed on Monday that Ramos’ three violations against Williams were correct under the Grand Slam rulebook.

“Carlos Ramos is one of the most experienced and respected umpires in tennis,” the statement said. “Mr Ramos’s decisions were in accordance with the relevant rules and were reaffirmed by the US Open’s decision to fine Ms Williams for the three offences.”

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Ramos also spoke out for the first time since the US Open. “It’s an unhappy situation but à la carte refereeing doesn’t exist,” the 47-year-old told Portugal’s Tribuna Expresso.

Many, however, are still fired up about Ramos’ controversial penalties, citing a number of male meltdowns in tennis history — such as Andy Murray kicking a ball toward an umpire’s head during the 2016 Cincinnati Masters in Ohio, or Roger Federer telling umpire Jake Garner “Don’t [expletive] talk to me in 2009 — and suffering no consequences.

“When a woman is emotional, she’s ‘hysterical’ and she’s penalized for it,” tennis legend Billie Jean King tweeted after the match on Saturday. “When a man does the same, he’s ‘outspoken’ & there are no repercussions.”

Sexisim in tennis has been an ongoing issue, particularly when it comes to pay parity. In 2016, tennis official Raymond Moore stepped down as director of BNP Paribas Open tournament for saying female tennis pros “ride the coattails of the men.” His remarks were slammed by top players like Williams and King.

And financially, women tennis players are making far less. Federer earned a combined $67 million for playing and endorsements in 2015, followed by Novak Djokovic with $48 million and Rafael Nadal with $32.5 million while women players like Maria Sharapova and Williams earned less than $30 million each, according to Forbes.

Plus, the sport has been accused of policing what women wear. U.S. Open officials gave a code violation to French tennis player Alizé Cornet last month for briefly taking her shirt off on the court because it was on backwards, revealing her sports bra — a call many deemed sexist. The U.S. Tennis Association issued an apology the next day, saying it “clarified the policy to ensure this will not happen moving forward.”