Microsoft has paused distributing its Meltdown and Spectre security updates for some older AMD machines after reports of PCs not booting. Microsoft’s support forums have been full of complaints from PC owners with AMD processors, and the software giant has acknowledged the issues today. Microsoft is blaming AMD’s documentation for the unexpected problems.

“Microsoft has reports of customers with some AMD devices getting into an unbootable state after installing recent Windows operating system security updates,” says a Microsoft spokesperson. “After investigating, Microsoft has determined that some AMD chipsets do not conform to the documentation previously provided to Microsoft to develop the Windows operating system mitigations to protect against the chipset vulnerabilities known as Spectre and Meltdown.”

Microsoft is now preventing AMD PCs from receiving updates, to stop machines from getting into an unbootable state. Microsoft is working with AMD to resolve the problems and continue issuing updates to AMD PCs soon, and affected owners will need to visit Microsoft’s support site for fixes to get machines back into a bootable state. The hiccup is an embarrassing issue for both AMD and Microsoft, just as the industry as a whole continues to deal with the fallout from the Meltdown and Spectre CPU flaws.

AMD confirmed the issues in a statement to The Verge. “AMD is aware of an issue with some older generation processors following installation of a Microsoft security update that was published over the weekend,” says an AMD spokesperson. “AMD and Microsoft have been working on an update to resolve the issue and expect it to begin rolling out again for those impacted shortly.”

Update 8:50PM ET: AMD statement added.