Apple says it has identified an issue where the “unlock with Apple Watch” feature might not work with its new iPhone 13 devices. A new note on its support page describes the problem:

You might see “Unable to Communicate with Apple Watch” if you try to unlock your iPhone while wearing a face mask, or you might not be able to set up Unlock with Apple Watch.

On Friday, users on the r/AppleWatch Reddit board began reporting that they were seeing this problem, and some said they were able to use the Watch unlock feature with other iPhone models, including the iPhone 11 Max.

Apple introduced the ability to unlock an iPhone that uses Face ID with a paired Apple Watch earlier this year with the release of iOS 14.5. It comes in handy during a pandemic where face masks are recommended in many public places, making it hard for Face ID to recognize you.

The feature works on iPhone X and later, and requires both the iPhone and the Watch to have wi-fi and Bluetooth turned on. The Watch needs to have wrist detection turned on and be passcode-protected, and it has to be on your wrist and unlocked for the feature to work.

Apple didn’t say what’s causing the problem with iPhone 13 devices, just that it will be “fixed in an upcoming software update,” but not when to expect the update.

The support page note advises switching off the “unlock with Apple Watch” feature and using your passcode to unlock your iPhone 13 while masked in the interim.