             stepSize = Math.abs(viewport.getHorizontalScrollPositionDelta(
                 (increase) ? NavigationUnit.RIGHT : NavigationUnit.LEFT));
         }
-        super.step(increase);
+        super.changeValueByStep(increase);
         if (viewport)
             stepSize = oldStepSize;
     }   

    //  Overridden properties
    //
    //--------------------------------------------------------------------------

    /**
     *  The size of the track, which equals the width of the track.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 10
     *  @playerversion AIR 1.5
     *  @productversion Flex 4
     */
    override protected function get trackSize():Number
    {
        if (track)
            return track.width;
        else
           return 0;
    }
    
    override public function set viewport(newViewport:IViewport):void
    {

    }
    

    /**
     *  If <code>viewport</code> is not null, 
     *  change the horizontal scroll position for page up or page down by 
