There are countless things about the state of technology in 2019 that would startle a visitor from 2009, but this is up there: Microsoft will include a custom-built Linux kernel in the next version of Windows, it announced Monday at Microsoft Build.

Microsoft already offers Windows Subsystem for Linux for Windows users that want to run a Linux distribution on their PCs, but it has taken things a step further in building its own version of the most recent Linux kernel designed to work with Windows. “This marks the first time that the Linux kernel will be included as a component in Windows,” said Jack Hammons, program manager for the Linux Systems Group at Microsoft, in a blog post.

Microsoft said it will also release its Linux kernel, based on the most recent long-term stable release of the open-source operating system, back to the open-source community. Packaging the Linux kernel with Windows will allow software developers (regular people are not going to do this) to build and run Linux applications directly on their Windows PCs, which Windows users writing applications using popular Linux cloud tools like Docker will appreciate.

Rather than emulating the Linux kernel, Windows will now ship a full Linux kernel. Makes for a great developer system for those deploying to Linux servers https://t.co/aAccRoETM5 — Miguel de Icaza (@migueldeicaza) May 6, 2019

The announcement comes ten years after Microsoft blew minds simply by contributing driver software to Linux, which was a huge validation for the concept of open-source software licensing and the beginning of the end of Microsoft’s combative relationship with the Linux community. Since then, Microsoft has continued to embrace Linux, adopting it as part of its Azure cloud computing service in 2012 and making it a company priority under CEO Satya Nadella.

Those in the Windows Insider program will be able to get their hands on this new feature by the end of June, Microsoft said. Microsoft released its own version of Linux last year when it launched Azure Sphere, but a full Linux kernel running inside Windows is a much bigger step.