diff --git a/ChartingSpace/Viewport.js b/ChartingSpace/Viewport.js
index d51df170b..ff472c391 100644
--- a/ChartingSpace/Viewport.js
+++ b/ChartingSpace/Viewport.js
@@ -200,7 +200,7 @@ function newViewport () {
     if (thisObject.visible === false) { return }
     if ((event.ctrlKey === true || event.metaKey === true)) { return }
     let morePower = 1
-    let amount = event.delta
+    let amount = event.delta * MAC_AMOUNT_FACTOR
     if (event.buttons === 4) { morePower = 2 } // Mouse wheel pressed.
        /* We adjust the sensitivity for Mac Users */