diff --git a/src/java/org/lwjgl/opengl/MacOSXNativeMouse.java b/src/java/org/lwjgl/opengl/MacOSXNativeMouse.java
index 6b1af8c3..e13afde7 100644
--- a/src/java/org/lwjgl/opengl/MacOSXNativeMouse.java
+++ b/src/java/org/lwjgl/opengl/MacOSXNativeMouse.java
@@ -215,7 +215,10 @@ final class MacOSXNativeMouse extends EventQueue {
 			setCursorPos(x, y, nanos);
 		}
         if ( dz != 0 ) {
-            int wheel_amount = (int)(dy * WHEEL_SCALE);
+        		// if no vertical wheel events, then map the horizontal wheel event to it
+        		if (dy == 0) dy = dx;
+        		
+        		int wheel_amount = (int)(dy * WHEEL_SCALE);
             accum_dz += wheel_amount;
             putMouseEvent((byte)-1, (byte)0, wheel_amount, nanos);
         }