Kourtney Kardashian Points Out Kim Kardashian's Big Mistake on Her Birthday Card!

Kourtney Kardashian is hilariously putting her sister Kim Kardashian‘s mistake on blast!

The reality star and Poosh founder turned 42 years old on April 18, and shared a video of Kim K.’s birthday card she sent her.

Click inside to see mistake Kim Kardashian made while writing Kourtney Kardashian’s birthday card…

While writing Kourtney‘s birthday card, Kim made a bit of a blunder!

“So Kim thinks I’m 41,” Kourtney said in an Instagram Story, showing off Kim’s mistake writing “41″ instead of Kourtney‘s actual age, which is 42. “I guess last year really didn’t count.”

You can read some of Kim’s birthday card…

Kourtney also got a very explicit birthday wish from someone special.