Ruby 1.9 curses library on windows - detect arrow keys?

I have been using ncurses-ruby with Ruby 1.8 on Windows. Upon
upgrading to Ruby 1.9 I discovered that the built-in curses library
supports colour etc. so I switched to that (very easy). Unfortunately
unlike Ncurses, Curses.getch does not return anything for arrow keys
or function keys.

Am I missing something or is this a bug?