Hey now, who are you calling a baby mama?!
In the snapshot, Rob wrote, "My Beautiful baby mama @khloekardashian looking fine as always on the cover of @cosmopolitanUK!"
The 29-year-old beauty responded to the nickname slipup by reposting the image and writing, "In Robs world baby mama and sister mean the same thing."
But affectionate siblings aside, Khloé does look like a million bucks in her latest magazine spread.
The E! reality star opened up in the mag and shared that she was "excited" for this year to be over.
"I love the new year, new beginnings," she said in the February 2014 issue. "I need a good fresh start; I'm excited for this year to be over with…You only live once so let's make that one time perfect. We can't fix our mistakes and imperfections, so let's have fun. You get what you give out in life."
She also shared some of her goals for 2014 since losing 30 pounds over the course of the last several months.
"I've worked very hard on my body so I think now I can sex it up a little!" she gushed to the magazine. "My 2014 mission is to wear a crop top with jeans. I've never done that so it has to happen one day."
And it seems that she's definitely staying focused on her goals…she tweeted on Tuesday afternoon that she was working up a sweat with her sister Kendall Jenner shortly before her evening festivities.
"Last workout of 2013 with @KendallJenner #Fitness #GetItRight #BeyoncéInspired," she tweeted.
Don't forget to tune in to the season premiere of Keeping Up With the Kardashians on Jan. 19 at 9 p.m., only on E!