diff --git a/lib/OpenLayers/Control/Navigation.js b/lib/OpenLayers/Control/Navigation.js
index a54ac46823..10e1387121 100644
--- a/lib/OpenLayers/Control/Navigation.js
+++ b/lib/OpenLayers/Control/Navigation.js
@@ -211,7 +211,7 @@ OpenLayers.Control.Navigation = OpenLayers.Class(OpenLayers.Control, {
      */
     wheelChange: function(evt, deltaZ) {
         var currentZoom = this.map.getZoom();
-        var newZoom = this.map.getZoom() + deltaZ;
+        var newZoom = this.map.getZoom() + Math.round(deltaZ);
         newZoom = Math.max(newZoom, 0);
         newZoom = Math.min(newZoom, this.map.getNumZoomLevels());
         if (newZoom === currentZoom) {