See here for more detail: + https://community.notepad-plus-plus.org/topic/22471/recompile-your-x64-plugins-with-new-header + https://github.com/notepad-plus-plus/notepad-plus-plus/issues/11104#issuecomment-1025206468 Basically, just take from the Notepad++ repo and replace in your repo: + notepad-plus-plus/scintilla/include/Scintilla.h + notepad-plus-plus/scintilla/include/Sci_Position.h then recompile. I'm currently using Python 3.0.7-alpha - Need the Python 3.8 support. I suppose the PythonScript 1.5.4 release will have this issue as well. Cheers.