diff --git a/src/mouse.h b/src/mouse.h
index 995ca936..04b8b2dc 100644
--- a/src/mouse.h
+++ b/src/mouse.h
@@ -24,6 +24,12 @@ extern "C"
 		CENTER_BUTTON = kCGMouseButtonCenter
 	};
 	typedef CGMouseButton MMMouseButton;
+	
+	enum __MMMouseWheelDirection	{
+		DIRECTION_DOWN = -1,
+		DIRECTION_UP 	 = 1
+	};
+	typedef int MMMouseWheelDirection;
 
 #elif defined(USE_X11)