Index: emu/ser.c
===================================================================
--- emu/ser.c	(revision a2b296e578fac4820601c722f9616fc24f8ef3d4)
+++ emu/ser.c	(revision c523a671692f93971f1bebdecb014eff66dc72ab)
@@ -32,4 +32,6 @@
 #if defined EMU_WIN
 #define MOU_DIV 64
+#elif defined EMU_OS_X
+#define MOU_DIV 1
 #else
 #define MOU_DIV 4