[M100] Saving a ".BA"

[D10D3 Data]

I find that when I open a .BA file in BASIC I can't save it as a .BA. It
took me awhile to realize that I didn't actually need to save changes to
the file due to the miracle of static ram, but if I want to save a back-up
of a program before I make changes can I only do it as a .DO? Saving a
program as a .BA, even with a new file name, gives me an FC error.
-Jason