Microsoft has quietly revealed that it is blocking the Windows 10 version 1903/1909 upgrade if you’re using some older AV solutions.

“Microsoft and Avast [have] identified compatibility issues with some versions of Avast Antivirus and AVG Antivirus,” a Microsoft support document notes. “Any application from Avast or AVG that contains Antivirus version 19.5.4444.567 or earlier is affected.”

“To safeguard your upgrade experience, we have applied a hold on devices with affected Avast and AVG Antivirus from being offered or installing Windows 10 version 1903 or Windows 10, version 1909 until the application is updated,” the support document continues.

This isn’t particularly unique: Microsoft blocked Windows 10 upgrades because of out-of-date AV software in the past. And it’s run into trouble with AV vendors because of changes it’s made to Windows 10 as well: As you may recall, Kaspersky complained in 2016 that Windows 10 upgrades would actually disable existing AV solutions and use Microsoft’s instead. Microsoft admitted to the practice in 2017 and then changed Windows 10 so that it would no longer do so.

This blocker appears to be more innocuous, of course. And the workaround is simple enough: Just upgrade your AV to the latest version.