Mozilla is complaining on Windows 10 upgrade process to Microsoft. In an open letter published addressed to Microsoft CEO Satya Nadella, Mozilla CEO chided the Redmond, Washington-based company over the its apparent decision to take away choice and control from the user. He admits that his team tried to work it out with Microsoft, but it didn’t result in any meaningful progress.

To pressure Microsoft to “undo” its actions, Mozilla is encouraging users to tell the Windows 10 manufacturer to “hit Ctrl+Z” and bring back user choice.