--- native_midi/native_midi_win32.c
+++ native_midi/native_midi_win32.c
@@ -193,6 +193,7 @@ int native_midi_detect()
   MMRESULT merr;
   HMIDISTRM MidiStream;
 
+  MidiDevice=(getenv("SDL_MIDI_DEVICE") != NULL) ? atoi(getenv("SDL_MIDI_DEVICE")) : MIDI_MAPPER;
   merr=midiStreamOpen(&MidiStream,&MidiDevice,(DWORD)1,(DWORD_PTR)MidiProc,(DWORD_PTR)0,CALLBACK_FUNCTION);
   if (merr!=MMSYSERR_NOERROR)
     return 0;