diff --git a/libspark/audio.cpp b/libspark/audio.cpp
index 482b62a..c03349b 100644
--- a/libspark/audio.cpp
+++ b/libspark/audio.cpp
@@ -101,7 +101,11 @@ int map_volume(const int volume)
 	if (vol > 100)
 		vol = 100;
 
+#ifdef MARTII
+	vol = 64 - vol * 64 / 100;
+#else
 	vol = 63 - vol * 63 / 100;
+#endif
 	return vol;
 }