Twenty years ago, Jimmy Fallon portrayed a diehard Boston Red Sox fan who fell in love and celebrated the franchise’s long-awaited World Series title. So it may have caught some viewers off guard to spot him rooting for their elimination on Thursday night.

Boston won’t make another title run following a Game 3 loss to the New York Yankees. If falling to their bitter rival wasn’t bad enough, the ESPN broadcast showed the “Fever Pitch” star jumping up and down and pumping his fist during New York’s four-run fourth inning at Yankee Stadium.

Awful Announcing shared a clip of the moment on social media.

Fallon played a devout Red Sox fan in “Fever Pitch,” but the late-night talk show host was born and raised in New York. He explained in 2004 that he initially rooted for the New York Mets because his dad got tickets through his job, but he gravitated toward the Yankees once “Saturday Night Live” showrunner Lorne Michaels started hooking him up with good seats.

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Fallon eliminated any doubt over his baseball allegiance during a “Tonight Show” interview with actress and Los Angeles Dodgers fan Elizabeth Olsen in March.

“I thought you were a Red Sox fan because of your one movie or whatever,” Olsen said to laughter, unintentionally mocking the host’s film portfolio.

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“Two movies,” Fallon corrected. “You believed that I was a Red Sox fan? I should have gotten a nomination for that film. I’m a Yankees fan.”

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Fallon told Olsen he had the “worst time” watching the Yankees lose to the Dodgers in last year’s World Series. Unfortunately, he seemed to have more fun on Thursday night.

Not every actor takes the Yankees/Red Sox rivalry as seriously as Ben Affleck, who shut down “Gone Girl” production over his refusal to wear a Yankees cap. Fallon can continue betraying the Red Sox when New York plays the Toronto Blue Jays in the next round.

Featured image via Jan 8, 2017; Beverly Hills, CA, USA; Jimmy Fallon presents during the 74th Golden Globe Awards at Beverly Hilton.