Can't permanently choose to have Files as non-default

Though Files is a good file-manager, I also use other file-managers (I'm also not using Luna). Unfortunately, every time I do use Files, it shows the "Files isn't your default file manager" bar at the top, regardless of whether if have chosen the "Ignore" option. I would like there to be a way to permanently indicate to Files that I don't want it to be the default, and for it to no longer show this warning.