diff --git a/static/scripts/viz/trackster/tracks.js b/static/scripts/viz/trackster/tracks.js
index 4892613a0a0..cb7aa708b73 100644
--- a/static/scripts/viz/trackster/tracks.js
+++ b/static/scripts/viz/trackster/tracks.js
@@ -1070,11 +1070,10 @@ var TracksterView = Backbone.View.extend({
             var delta_chrom = Math.round(delta / view.viewport_container.width() * (view.high - view.low));
             view.move_delta(delta_chrom);
         // Also capture mouse wheel for left/right scrolling
-        }).bind( 'mousewheel', function( e, d, dx, dy ) { 
-            // Only act on x axis scrolling if we see if, y will be i
-            // handled by the browser when the event bubbles up
-            if ( dx ) {
-                dx *= 50;
+        }).bind( 'mousewheel', function( e, d, dx, dy ) {
+            // Only handle x axis scrolling; y axis scrolling is
+            // handled by the browser when the event bubbles up.
+            if (dx) {
                 var delta_chrom = Math.round( - dx / view.viewport_container.width() * (view.high - view.low) );
                 view.move_delta( delta_chrom );
             }