The just-turned 18-year-old gave mother Kris Jenner a blast from the past when she wore her old swimsuit from the 80s, which Kris was quick to remind her daughter about on Instagram.
"So THIS is where my vintage Body Glove bathing suit went!" the Kardashian matriarch captioned the photo (which shows her also in Mexico), joking that she was going to ground Kylie for borrowing it.
We have to admit, this is pretty dang cute. After all, parents do have the best style advice...