Apple today admitted that some iPhone 7 and 7 Plus models running iOS 11.3 or later may have a bug that disables the microphone during phone calls, MacRumors spotted through a leaked document. The few users with the affected devices may see their speaker button grayed-out when making calls or video chatting through FaceTime. The issue seems to only affect phones running that version of iOS or versions after 11.3.

Some users on Reddit and Twitter have reported experiencing such microphone issues in the past few months and the leaked document, sent out to its Apple Authorized Service Providers network, apparently confirms Apple is aware of the problem.

Apple is recommending these tech support workers tell customers to first unpair or turn off any Bluetooth devices and accessories that were connected to their iPhones, as a possible solution. If that doesn’t work, tech support is also advised to run audio diagnostics, which will show if the iPhone needs repair with alert messages like “accessory not supported” or “device could not detect dock.” Once a message like that appears, the tech support can start fixing the iPhone. It’s apparently not clear from the document what the actual software or hardware issue is, notes MacRumors.

Even if the user doesn’t have a warranty covered device, Apple is making an exception and its store employees at the Genius Bar will fix the issue without question. The document apparently doesn’t say if the repair is free. We’ve reached out to Apple for comment.