Twitter’s new ephemeral tweets, known as fleets, are supposed to last for only 24 hours. But a bug is causing fleets to not totally disappear, remaining accessible well past their expiration dates. First reported by TechCrunch, the bug allows fleets to be viewed and downloaded by other users, but without notifying the fleet’s author.

“We’re aware of a bug accessible through a technical workaround where some Fleets media URLs may be accessible after 24 hours,” a Twitter spokesperson said in an email to The Verge. “We are working on a fix that should be rolled out shortly.”

The “workaround” referenced appears to be a developer app that could scrape fleets from public accounts via Twitter’s API. The Twitter API doesn’t return URLs for fleets that are older than 24 hours, according to the company, and once the fix is rolled out, even if someone has a URL for active fleet, it won’t work after the expiration point.

And while fleets are only visible on users’ timelines for 24 hours, Twitter stores fleets on its back end for up to 30 days, longer for fleets that violate its rules and may require enforcement action, the company says. During that 30 day period, a fleet is available in a user’s Twitter Data downloads as long as Twitter is retaining a copy. The “seen by” action is typically only available when someone views a fleet via the Twitter app.

Twitter is a bit late to the disappearing content party— fleets are essentially its version of Instagram or Snapchat stories, They allow mobile Twitter users to briefly share text, videos, images, or other tweets. They’re not meant to be retweetable and you can’t directly “like” a fleet, but you can reply to one by tapping on it, which sends a direct message to the fleet’s creator.

Update November 22nd, 10:56 AM ET: Added comment from Twitter and additional details