Kylie Jenner may have shaved $1.3bn (£930m) off Snapchat's market value with a single tweet saying she no longer used the social media app.
Shares in Snap, the app's parent company, closed 6% down on the US stock market after Jenner's post.
"Sooo does anyone else not open Snapchat anyone? Or is it just me... ugh this is so sad," Jenner tweeted to her 24 million followers.
The tweet appears to have been a reference to the app's recent redeisgn, which has in geneally been slated by users.
Jenner, the half-sister of Kim Kardashian, later tweeted again in defence of the platform.
"Still love you tho snap ... my first love," she wrote.
More that one million people signed a Change.Org petition calling for Snapchat to revert to its previous design, labelling the new version too difficult to use shortly after its launch.
In response to the online petition, the company promised further changes to improve the experience.
"We hear you, and appreciate that you took the time to let us know how you feel," the firm wrote in a post on Change.org.
Snapchat is facing intense pressure from Facebook and the line of apps in its ownership - including WhatsApp and Instagram - which have adopted Snapchat-like features in recent years to try and entice users to switch services.
Snapchat has around 180 million users, significantly fewer daily users than Instagram, which currently has more than 500 million.