On season 17, the sisters fought over Kourtney's "boundaries" when it comes to filming their family's reality show

The tension between Kim Kardashian West and her sister Kourtney Kardashian on Keeping Up with the Kardashians isn’t over yet.

During an appearance on the Ellen DeGeneres Show on Tuesday, Kim, 39, opened up about the drama that played out between them on season 17 of the show, revealing that it carries over into the upcoming season 18.

“Kourtney and I, we just went to Japan together. We’ve really taken the time to hear each other out and listen,” she said. “What sucks is that season 18 will come out soon and it gets worse before it gets better. But her and I have healed and have talked about everything and really come to an understanding.”

Season 17 saw serious tensions arise between the Kardashian sisters over Kourtney’s “boundaries” when it comes to the show, with Kim and Khloé Kardashian, 35, complaining about having to “pick up the slack” in moments when Kourtney, 40, refused to film. At one point, Kim even threatened to fire Kourtney, though sources have told PEOPLE that this isn’t actually possible since all three sisters are equal-level executive producers.

Kourtney, Khloe, Kim Kardashian
From left: Kourtney Kardashian, Khloé Kardashian and Kim Kardashian West
| Credit: AFF-USA/Shutterstock

Speaking to Ellen DeGeneres, Kim explained that Kourtney “likes [the show], but she only wants to film when she feels like it.”

“If one family member goes on vacation a lot or takes time off a lot, the other family members have to step in and take over those hours,” she said. “So for the past year, Khloé and I have been taking over her hours, working, because we need content to make the show.”

“So Khloé and I have been really frustrated that we’ve been working longer and we have kids and a lot of stuff going on, and it’s been exhausting for us when she hasn’t taken that into consideration without making a decision of what she wants to do,” she continued. “Stay on the show, not, but to be in this limbo and have us do this for so long is frustrating.”

“We’ve come to the conclusion that [Kourtney will] film a little bit,” she added, before clarifying, “I don’t even know if we have a conclusion, actually. It’s always up in the air.”

“But we’re in a good place about respecting each other’s space,” she said. “And if someone doesn’t want to be on the show, we obviously want them to have that mental break and live their life exactly the way that they want.”

Kim Kardashian West Ellen DeGeneres
Credit: Michael Rozman/Warner Bros

On Sunday’s season finale, Kourtney grappled with her future on the family’s long-running reality show, confessing she may have reached her limit.

“I have three kids that are my priority more than the show,” she said. “What I’m saying is I’m getting to the point where I’m not happy. Everyone has their breaking point. Life is short. It’s not all about filming this show.”

“It’s not okay that I feel like I’m at my breaking point,” she continued. “I need a break and I don’t want to film anymore.”

RELATED VIDEO: Kim Kardashian Threatens to Fire Kourtney from KUWTK for Hiding Her ‘Personal Life’ — ‘She’s Out’

During an appearance on Entertainment Tonight last month, Kourtney revealed that she would be taking a step back from the show to focus on her children with ex Scott Disick — sons Mason, 10, and Reign, 5, and daughter Penelope, 7.

“I just decided to spend more time as a mom and put more of my energy there,” she explained, adding, “But I’m not saying goodbye.”

A premiere date for season 18 of KUWTK has not yet been announced. Ellen airs weekdays (check local listings).