One of the most popular social media features invented in past five years is the story. the chronological procession of photos, video, and text that erases itself after 24 hours. It was invented by Snapchat and borrowed by Instagram and now Facebook. 250 million people use the feature on Instagram every day. Now Instagram is borrowing another feature from Snapchat. In a test starting this week, the company will sometimes alert you when someone takes a screenshot of your Instagram story.

It makes sense, in a way. Stories are confessional and disposable by design. On Instagram, you can’t link to a web page from your story; you just have to sit there and watch it. But there’s nothing to keep someone from taking a screenshot of this private form and sending it to their friends or posting it online. So without an easy way to block people from using the screenshot function, which is controlled by a phone’s operating system. Instagram is borrowing from Snapchat and doing the next best thing.