Video: Rob Kardashian Slams Scott Disick: "He's an Alcoholic!"

Has Scott Disick reverted back to his hard-partying ways?

As a new clip from Sunday's Keeping Up With the Kardashians shows, Kourtney Kardashian's beau may have won over her mom, Kris Jenner, in recent months, but her brother, Rob Kardashian, is still anti-Scott.

PHOTOS: See Rob and his siblings as kids

Turns out that Disick, 28, is the real reason why Rob, 24, has yet to visit the couple's new home five months after they moved in!

Checking out the digs for the first time in an effort to hang out with his nephew, Mason, 18 months, Rob whines to Kourtney about a stomach ailment that Kourtney declares to be the result of excess drinking. (Rob underwent an emergency appendectomy in March, around the time this scene was filmed.)

VIDEO: Why Kourtney won't marry Scott

"The reason I don't come over here is because of Scott. He's an alcoholic!" Rob shoots back. "He's a negative person in my life. Like, [he] has a kid. Show me that you're mature and show me you're mature enough to have a kid with my sister."

Entering therapy for his addiction issues in 2010 -- bringing reality cameras along -- Disick has been open about his drinking in the past.

VIDEO: Kris Jenner walks in on Scott "butt naked"

"[Kourtney] doesn't really always 100% understand that it's a real disease that I have, and it's not just something that I can turn off and on," Disick has said. "But now that I have a little baby, I don't really want to play any of these games. I just want to be with her and see my son grow."

Check out the clip above for more of Rob and Kourtney's discussion, and tell Us: Do you think Scott has changed his ways?

Keeping Up With the Kardashians airs Sunday at 10 p.m. (EST) on E!

By Allison Corneau for Us Weekly. For more Channel Surfing, click here.