It doesn’t look like Scott Disick had a happy birthday.

The Keeping up With the Kardashians star hit Sin City over the weekend to celebrate his upcoming birthday, but judging from the photos taken during the party held in his honor at the popular 1 Oak nightclub on Saturday, May 20, it didn’t look like Scott was having a good time without his ex-girlfriend, Kourtney Kardashian.

scott disick birthday party 2017 getty

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"He appeared to be enjoying himself but wasn't his usual happy-go-lucky self in what has become his favorite Las Vegas nightclub," a source revealed to Us Weekly.

Scott won’t officially turn 34 years old until next week, but he still rounded up a small group of friends to kick off his birthday week. He started partying early in the afternoon at the Liquid Pool Lounge at Aria Resort & Casino with Brody Jenner and a few other pals. They were also spotted having dinner at Stack restaurant before they arrived at 1 Oak.

scott disick birthday party 2017 getty

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The father-of-three usually celebrates his birthdays at the celeb-friendly club, but the biggest difference this year is that his longtime on-again, off-again girlfriend Kourtney Kardashian was not in attendance because it seems like they’ve split up for good. The exes finalized the end of their nearly decade-long relationship during a family trip to Costa Rica, which played out on the current season of KUWTK.

Kourtney has since moved on with her rumored boyfriend, 24-year-old model Younes Bendjima and even though Scott has also been spotted out on dates with various models, sources revealed to Life & Style that he can’t stand to see his baby mama with another man.

"Scott will do anything to sabotage Kourtney’s relationship, including showing up wherever Kourtney and Younes are hanging out together,” the insider said. “He’s also been asking around, trying to get some dirt on Younes so he can bring it back to Kourt and persuade her to dump him."