Some Windows 10 users are upset today after Microsoft suddenly deactivated their Windows installations, resulting in “Activate Windows” nags. Microsoft has confirmed the error and said a fix is in the way.

Update: Microsoft’s Jeff Jones told Bleeping Computer this problem is now fixed and affected PCs will automatically become activated again sometime in the next 24 hours. Mary Jo Foley over at ZDNet points out that you can head to Settings > Update & Security > Activation > Troubleshoot to fix it immediately.

This problem seems to affect Windows 10 Professional users who upgraded from Windows 7 Professional or Windows 8 Professional. Microsoft’s activation servers suddenly decided their digital licenses were no good and deactivated them. After running the activation troubleshooter, Windows 10 said their systems should actually be using Windows 10 Home instead of Windows 10 Professional. That’s what many Windows 10 users on Reddit report happened to them.

Affected Windows users can expect to see an annoying “Activate Windows” watermark over the bottom right corner of the desktop, distracting from work, gaming, or whatever else they’re doing on their PCs.

This is just what happens if you don’t activate Windows 10, although we’ve never seen this suddenly happen to people with legitimate Windows 10 licenses before.

A Microsoft MVP and forum moderator confirmed the problem. Here’s what Microsoft chat support said:

Microsoft has just released an Emerging issue announcement about current activation issue related to Pro edition recently. This happens in Japan, Korea, American and many other countries.I am very sorry to inform you that there is a temporary issue with Microsoft’s activation server at the moment and some customers might experience this issue where Windows is displayed as not activated. Our engineers are working tirelessly to resolve this issue and it is expected to be corrected within one to two business days

So, if you’ve run into the problem, hold tight and Microsoft will fix it for you. Don’t install Windows 10 Home, as Windows 10 is asking you to. Wait a few days—while dealing with activation nags the whole time—and hope Microsoft fixes the bug on schedule.

Yes, it’s yet another Windows 10 bug! Between deleting people’s files, a .zip file data loss bug, and broken file associations lately, we really wish Microsoft would slow down, stop breaking things, and release a stable operating system.

By the way, did you realize that your PC was constantly phoning home to confirm your activation with Microsoft, and that a bug with Microsoft’s servers could break the activation? You probably didn’t, but that’s apparently how it works. It’s all fine until Microsoft breaks things—which it just did.

If you want to check your PC’s activation status, you can do so from Settings > Update & Security > Activation. If it says Windows is activated, you’re fine. But you don’t even need to check this—believe us, if Windows 10 isn’t activated, Windows will be sure to nag you about it.