Microsoft’s Windows Hello face unlock feature no longer works in dark rooms, and it’s not a bug. Microsoft quietly made the change to Windows Hello in April, in order to fix a vulnerability with Windows Hello spoofing. Fixing the security flaw has now removed key functionality from Windows Hello in Windows 11.

Windows Central spotted April’s change after some Surface Laptop users have noticed they can no longer use their face to sign into their laptop in a dark room. “After installing this update or a later Windows update, for enhanced security, Windows Hello facial recognition requires color cameras to see a visible face when signing in,” says Microsoft in its April Windows Update patch notes.

You can get Windows Hello to continue working in a dark room if you disable your webcam in the Windows 11 Device Manager, but then this means you can’t use your camera in any apps or video calls. It’s a workaround if you only use the camera to unlock your laptop, but most people will want the camera to function inside video calling apps.

Microsoft uses a combination of the color camera and IR sensors to detect a face for its Windows Hello feature. The security vulnerability, discovered by the Nanyang Technological University, was rated “important” by Microsoft, and hasn’t been publicly disclosed or exploited. Microsoft even suggests it’s “less likely” that a malicious actor would exploit this locally on a device.

We’ve reached out to Microsoft to see whether the company might get Windows Hello working in the dark again in the future, and we’ll update you accordingly.