Past Keeping Up With the Kardashians teasers have shown us Kourtney Kardashian and Kim Kardashian’s explosive, physical fight — but now we finally know what started it. A new teaser for the E! show, which drops Thursday, March 26, takes us into the few moments before the sisters start swinging at each other. As it turns out, the blowup begins when Kim once again suggests that Kourtney doesn’t work hard — and Kourt tells her little sis to “change the narrative” in the way she thinks, fast.

“You act like I don’t do s–t,” the eldest Kardashian daughter slams. “Do you know all I f–king — You have this, this narrative in your mind of —” When Kim, 39, cuts her off, Kourt, 40, threatens, “I will literally f–k you up. If you mention it again? Literally, shut the f–k up. … But honestly, change the narrative in your mind. I work my f–king ass off.”

Kourtney Kardashian Tells Kim Kardashian to Change the Narrative About Her Work Ethic on KUWTK

While speaking to the camera, the mother of three continues, “I just, I don’t want to hear this narrative anymore about this work ethic, and she’s the only one with work ethic, and she’s doing this, this and this, as if she’s better because she works more or because … It’s such bulls–t. We don’t all have to do things the same way.”

The argument escalates when the Poosh founder pelts her younger sister with a plastic bottle — but we’ve seen the tension between these two simmering for months. In the last season, it seemed Kim and Khloé Kardashian were constantly calling out their older sister. In one episode, they even went to talk to producers to try and get her fired from the show.

After Kim and Koko decided they’d been filming more than their fair share because they’d had to pick up Kourt’s slack, they brought mom Kris Jenner into the conversation so she could hopefully settle the issue. But Kris, 64, had her eldest daughter’s back. She knew better than most just how much Kourtney let the cameras into her life — in particular, her love life with Scott Disick.

But the back and forth was beginning to turn Kourt off the show entirely. “I just don’t want to film every day and have it be a toxic environment,” she said on KUWTK. “You know, I just need my sisters to stop harping on it. Just like either accept that that’s what it is or, like, move on. We are all different people, we have different things that are important to each of us. My well-being is more important than the show. I’m not giving in.”

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