Some Windows 7 and Windows 8.1 users this week started reporting they were being forced to upgrade to Windows 10, even though they had not reserved a copy nor indicated in any way they wanted to upgrade. We reached out to Microsoft asking why users were being forced to install Windows 10, and the company replied that the issue came down to an optional update in Windows Update being checked by default. The company has now reverted the checkbox, calling the whole snafu “a mistake.”

For one year, Microsoft is offering free Windows 10 upgrades to Windows 7 and Windows 8.1 users — one of many strategies the company is employing to achieve its goal of 1 billion devices running Windows 10 “in two to three years.” Microsoft is even downloading Windows 10 in advance so that users will be more likely to complete the free upgrade process.

Yet the company went too far this time, and is now saying it was all an accident. After all, an optional update should not, by definition, be checked by default.

“As part of our effort to bring Windows 10 to existing genuine Windows 7 and Windows 8.1 customers, the Windows 10 upgrade may appear as an optional update in the Windows Update (WU) control panel,” a Microsoft spokesperson told VentureBeat. “This is an intuitive and trusted place people go to find Recommended and Optional updates to Windows. In the recent Windows update, this option was checked as default; this was a mistake and we are removing Windows 10 from Windows Update for users that have not reserved a copy of Windows 10.”

Microsoft has already received many complaints about Windows Update downloading the Windows 10 installation files. Starting the setup process is a different story altogether. Thankfully the company has addressed the issue now, and has managed to get a better handle on how its Windows Update tool is supposed to work.