Google unveiled the Pixel 4 signature features months ahead of the phone’s launch, confirming rumors that said the phone will be Google’s first handset to support 3D face recognition. At the time, Google also announced that its face unlock system would use a novel approach, relying on Soli radar chips to enhance the functionality, and suggested that its Face ID alternative might be better than alternatives. Once the Pixel 4 was launched, users discovered that face unlock had one critical flaw when compared to Apple’s, as it didn’t have a Require Attention option — that someone could unlock your phone by holding it against your face while you sleep. That’s the kind of security oversight that can be fixed via a software update. But it turns out that software updates can have negative effects on face unlocks, as some users haven’t been able to use the feature to unlock their handsets.

The feature isn’t widespread, Android Police reports, but there have been plenty of reports online since November detailing the issue. Some Pixel 4 owners observed two distinct errors when attempting to unlock the phones, considering the prompts they received — Can’t verify face. Hardware not available and Can’t verify face. Try again.

Many of them first experienced the problem after installing the December security update, although it’s not clear what causes the issue.

This is the kind of error iPhone users never had to worry about. Sure, Face ID can fail to recognize your face in certain conditions, and it might take some people more time to train themselves to the Face ID experience. But iOS updates, including beta releases, have not broken Face ID functionality.

Fixes, like deleting face data and reconfiguring face unlock; and restarting the Pixel 4 in safe mode, don’t work. A factory reset might fix the issue, but it’s not guaranteed. Google is aware of the reports and it’s looking to fix the issue, Android Police notes. Fixing the newest Pixel phone is an annoying Pixel tradition, of course.

If face unlock doesn’t work on your Pixel 4, all you can do is use a pin to unlock the display until a permanent fix is implemented, as the Pixel 4 phones don’t have any other authentication method available. You should still protect your handset with a password, even if face unlock fails, and you should definitely install all the security updates that Google releases, even if you risk running into unexpected issues like the face unlock bug.

Chris Smith started writing about gadgets as a hobby, and before he knew it he was sharing his views on tech stuff with readers around the world. Whenever he's not writing about gadgets he miserably fails to stay away from them, although he desperately tries. But that's not necessarily a bad thing.