This anomaly was noticed by Windows testers shortly after Microsoft rolled out its latest Dev Channel build of Windows 11 on Friday afternoon. The bootup sound contained in the .WAV file within imageres.dll was unexpectedly replaced with the Windows Vista startup sound in preview build 26200.5651.

Microsoft promptly acknowledged the error and included a note in its release documentation for the latest Dev Channel build. “This week’s release includes a nostalgic moment by playing the Windows Vista boot sound instead of the Windows 11 boot sound,” explained the Windows Insider team. “We are working on a resolution.”

It’s not clear how such a mistake even happened, but Brandon LeBlanc from the Windows Insider team joked on X that he “went in and had some fun with the sound files in Windows and thought folks needed a blast from the past,” before confirming that it was actually just a bug.

Perhaps one of Microsoft’s Windows engineers was reminiscing too much about Windows Vista, in a week when Microsoft made it clear it thinks Apple’s new Liquid Glass design bears some resemblance to its Aero Glass look in Windows Vista.