Kris Humphries didn't exactly get off on the right foot with fiancee Kim Kardashian's older sister, Kourtney.

In a sneak peek from Sunday's episode of Keeping Up With the Kardashians, Kim, 30, puts her NBA player beau, 26, on speakerphone to chat with Kourtney prior to their Bora Bora vacation.

"Kourtney, just because you have a kid and you don't do anything fun does not make you mature," Humphries tells Kourtney, 32, out of the blue.

During her confessional, Kourtney (mom to Mason, 20 months) admits that "none of us have spent any serious time with Kris. He's very sarcastic and I just don't know what to make of him yet."

Will Humphries win Kourtney's seal of approval? Watch Keeping Up With the Kardashians when it airs Sunday at 10 p.m. EST on the E! Network.