diff --git a/src/audio/mint/SDL_mintaudio.c b/src/audio/mint/SDL_mintaudio.c
index e63671267..b98bb3242 100644
--- a/src/audio/mint/SDL_mintaudio.c
+++ b/src/audio/mint/SDL_mintaudio.c
@@ -42,9 +42,9 @@
 SDL_AudioDevice *SDL_MintAudio_device;
 Uint8 *SDL_MintAudio_audiobuf[2];	/* Pointers to buffers */
 unsigned long SDL_MintAudio_audiosize;		/* Length of audio buffer=spec->size */
-unsigned short SDL_MintAudio_numbuf;		/* Buffer to play */
-unsigned short SDL_MintAudio_mutex;
-unsigned long SDL_MintAudio_clocktics;
+volatile unsigned short SDL_MintAudio_numbuf;		/* Buffer to play */
+volatile unsigned short SDL_MintAudio_mutex;
+volatile unsigned long SDL_MintAudio_clocktics;
 cookie_stfa_t	*SDL_MintAudio_stfa;
 
 /* MiNT thread variables */