Kim Kardashian West just made a gender reveal slip so many moms can relate to. Although she wasn't planning on announcing whether her surrogate is carrying a boy or a girl just yet, the mom of Saint and North West got a little caught up while telling a story on the set of The Ellen DeGeneres Show today, according to E!

Kim was filling Ellen in on North's reaction to a haul of baby gear at a recent baby shower and forgot to omit one important word from the re-telling.

“She was opening [the baby's gifts] up the next day and she said, 'Mom, Baby Sister's not here. I think I need all of her toys in my room. I'll play with them and just make sure they're okay for Baby Sister.'"

Ellen's response is what we're all thinking.“You just told us it's a girl!"

Kim wasn't worried about her oops and moved on with a laugh, revealing that North is super excited to be a big sister.

“Let's see if it lasts," she told the talk show host.

“I did explain to her, 'Okay, at 4:00 in the morning, when you come in my room, I'm going to have to be with Baby Sister—I have to feed her.' We'll see how it goes."

Hopefully Kim's next slip will be the name of Baby Sister, because the world can't wait to hear what she and Kanye will choose to call North and Saint's new sibling. Kim says the couple haven't picked a name yet, though.

The soon-to-be mom of three revealed that North wants to name the baby Star West, but mom's “not vibing on it," despite that fact that it fits all her name rules.

"Short, easy to spell, one syllable," Kim told Ellen.

There's a lot of names that fit the bill but only a few weeks left to choose one. Us Weekly reports the couple's surrogate is due before Christmas.