How to use Checkbox with Tree

[newbie newbie]

Hi,
I am trying to implement a tree. I want users to be able to select leaf
nodes by clicking on checkbox at each leaf nodes. But it is currently not
working with the checkbox. The tree cannot expand.

Here is my tml code fragment

<t:zone t:id="treeZone" id="treeZone">
     <t:tree t:id="Tree" t:model="treeModel" t:node="treeNode" >
          <p:label>
                <t:if test="treeNode.leaf">
                        <input t:id="leafNode" t:type="checkbox"
value="leaf" />
                        ${treeNode.label}

                    <p:else>
                         ${treeNode.label}
                    </p:else>
                </t:if>
           </p:label>
       </t:tree>
</t:zone>

If I take away <input t:id="leafNode" t:type="checkbox" value="leaf" />,
then the tree can expand. But I need the checkbox. Any help would be
appreciated. Thanks.