diff --git a/src/s_sound.c b/src/s_sound.c
index a494990407693568ed6ddda9ad042784dd3d8c66..0235d8376ce791b7859ab8997153709a2b336848 100644
--- a/src/s_sound.c
+++ b/src/s_sound.c
@@ -61,7 +61,9 @@ static void GameMIDIMusic_OnChange(void);
 static void GameSounds_OnChange(void);
 static void GameDigiMusic_OnChange(void);
 
+#ifdef HAVE_OPENMPT
 static void ModFilter_OnChange(void);
+#endif
 
 static lumpnum_t S_GetMusicLumpNum(const char *mname);