Kourtney Kardashian Suffers Wardrobe Malfunction at Kendall Jenner's Birthday Party

Darn you, see-through clothing!

Darn you, see-through clothing!

Kourtney Kardashian suffered a wardrobe malfunction at Kendall Jenner's 20th birthday party in West Hollywood, California on Tuesday.

WATCH: EXCLUSIVE: Scott Disick Gets a Visit in Rehab From Kris Jenner and His Kids, But Not Kourtney Kardashian

As you can see, the 36-year-old looked on point as usual, despite the sheer fabric on her top exposing a little nipple. Also, please note that sister Khloe's bob is looking choice as hell right now.

The proud older sister was clearly having the most fun, as she went a little nuts with the Instagram posts congratulating Kendall on her big day.

WATCH: Kourtney Kardashian Flaunts Her Amazing Bikini Bod While Scott Disick Spends 'Boy Time' in Mexico

"I have the weirdest pics of us in my phone! My baby Kenny have a magical birthday," Kourtney wrote on one post.

From the look of things, it was one big party.

WATCH: Kourtney Kardashian and Kids Dress Up As Cutest Superhero Family for Halloween

Aww, what a proud sister!

Kourtney has been killing it lately, after her split from longtime boyfriend Scott Disick in July. Despite their problems, Kourtney has been adamant about not keeping the couple's three children, 5-year-old Mason, 3-year-old Penelope and 10-month-old Reign, away from their father. Last week, the kids, along with grandma Kris Jenner, went to visit Scott in rehab, and even though Kourtney wasn't there, a source tells ET it was her idea.

WATCH: Kourtney Kardashian Reacts to Scott Disick's 18-Year-Old Model Girlfriend

Watch the video below for all of Kourtney's killer post-breakup looks!