Help needed in resolving warnings while migrating to flash 4.6

Getting the below error in FlashBuilder 4.6:

1067: Implicit coersion of a value of type mx.controls:Tree to an unrelated type mx.controls:Tree

The line of code is below which is there in QueryTreeAs.as:

ModelLocator.getInstance().queryTree=queryTree;

where queryTree is a component in a different mxml file - QueryTree.mxml. Like the below one:

<?xml version="1.0" encoding="utf-8"?>

<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml"

    width="100%"

    height="100%"

    name="query"

    creationComplete="init()">

  <!--<mx:Style source="/assets/styles.css" />-->

  <mx:Script>

  <![CDATA[

  include "QueryTreeAs.as"

  ]]>

  </mx:Script>

  <mx:Tree y="0"

  id="queryTree"

  width="100%"

  height="100%"

  showDataTips="true"

  dataTipFunction="getDataTipLabel"

  labelFunction="tree_labelFunc"

  showRoot="true"/>

</mx:Canvas>

Any pointers to resolve this issue would be helpful!