Instagram confirms that a bug this morning mistakenly rolled out a massive change to its feed that replaced the traditional scrolling with horizontal tap-to-advance, like with Stories. In October, TechCrunch reported Instagram was testing tap-to-advance for browsing through Explore posts. But many users woke up to a shock this morning when their familiar vertical swipe stopped advancing the main feed. Many users immediately complained that the gesture felt awkward and annoying.

“Due to a bug, some users saw a change to the way their feed appears today. We quickly fixed the issue and feed is back to normal. We apologize for any confusion,” an Instagram spokesperson tells TechCrunch. The company confirms it’s still testing the navigation style in Explore.

Instagram was attempting to test the feature with a small percentage of users, but the bug caused a much broader rollout to a few orders of magnitude more people than planned, according to head of Instagram Adam Mosseri. Users can restart their Instagram and the change should disappear.

Sorry about that, this was supposed to be a very small test but we went broader than we anticipated. 😬 — Adam Mosseri (@mosseri) December 27, 2018

Tap-to-advance makes it easier to move between posts with them staying fully in view, compared to scrolling where it can take some adjustment to make sure the top or bottom of a post isn’t cut off. But scrolling revealed the author of a post first, then the content, then the caption, which is a sensible and intuitive way to browse. Tap-to-advance could send users’ eyes flitting around the screen in an exhausting manner. But most importantly, people have spent eight years growing accustomed to scrolling the Instagram feed. Suddenly breaking that behavior pattern was sure to piss people off.

It’s possible that Instagram could still bring tap-to-advance to the main feed in the future. But given how angry the responses were, it might now think twice unless the data shows the change makes people spend a lot more time in the app.

Here’s a look at how tap-to-advance in the feed worked, and the alert users got about how it works.