As anybody with sisters (or siblings) will understand, sometimes you’re a bit irrationally mean to each other, but it’s generally done out of love.

Still, in a teaser for the upcoming season of Keeping Up With the Kardashians, Kourtney might have gone too far.

Let us set the scene for you.

Kim, Kourtney and Khloe were having a meeting at Khloe’s house, when it became obvious that sister Kourtney just wasn’t in the mood.

There were warning signs: the 39-year-old was on her phone and she came in late, but Kim and Khloe continued to prod her – as sisters do.

“Thanks for being so present,” joked a sarcastic Kim.

And that’s when Kourtney snapped – you can almost pin point the exact moment.

Suffice to say, Kourtney was not having a good day. Image: E! Network.

"Who let you choose black covers for your furniture? Disgusting," she said.

"Usually people choose a colour that's neutral to their floor."

Retorting her insult, Khloe responded: "When I come into your house, I'll make sure to say just a critical comment."

You can watch the sisterly squabble here:

While we're not sure about the origins of these offensive black furniture covers, or exactly what caused Kourt's bad mood, Khloe then shared this touching sentiment with the behind-the-scene's crew.

"If I wasn't pregnant, I would have probably drowned you in the pool," she said, with a few expletives thrown in.

Could these have been the offending "furniture covers" Kourtney was talking about? Image: Instagram @khloekardashian.

So in review:

Black furniture covers are a strict no-go... and don't let anyone tell you otherwise.

And you probably don't want to get in a fight with Kourtney Kardashian, because she's terrifying.

As you were.