Kim Kardashian and Caitlyn Jenner were known for sharing a very close relationship, but the preview of the upcoming episode of I Am Cait tells us a different story.

In the promo, North West's mother can be seen talking tough with Caitlyn, who is "throwing shades" at the whole Kardashian clan in her show.

"You look amazing. It's your time," the Keeping up With The Kardashians star told her former step-father adding, "But you don't have to bash us on your way up."

Hollywood Life reported that the argument was "pretty intense than what was shown in the episode preview", as the 34-year-old reality TV star was not happy with Jenner's comments about her mother Kris.

"When Caitlyn started making derogatory comments about Kris in the Diane Sawyer interview and then in Vanity Fair, Kim felt as though she crossed the line," a source told the website.

"The fight on I Am Cait paled in comparison to what Kim really said to Caitlyn. That confrontation for the show was basically a watered down recreation of how Kim really went after Cait. Caitlyn was refusing to talk to Kris, so Kim had to speak for her and she really let Caitlyn have it. Kim is happy for Caitlyn, but she is not going to let her diss Kris and hurt their family brand while promoting her own show," the same source added.

In her Vanity Fair interview, the 65-year-old former Olympic athlete accused Kris of "mistreating" her during their marriage.

"The first 15 years I felt [Kris] needed me more because I was the breadwinner. Then, really around [the time of KUWTK], when that hit and she was running the whole show and getting credit for it and she had her own money, she didn't need me as much from that standpoint…," Caitlyn told Vanity Fair and added, "I think in a lot of ways she became less tolerant of me. A lot of times she wasn't very nice. People would see how I got mistreated. She controlled the money, all that kind of stuff."

I Am Cait is an eight-episode docu-series following Caitlyn's life and will return with episode 2 next Sunday.