Radtreeview Font size increases when collapsing

[win]

Hi,
Im using this RadTreeview when i click on the expand button to view the child nodes the font of the child nodes are increasing for each node.
Ex:
Root(xx-small)
- Child1(x-small)
  -Child1-1(Small)
   - child1-1-1(Medium)
I want to display everything in xx-small font.

<div style="font-size: xx-small">
                  <telerik:RadTreeView ID="rtvTreeView" CheckBoxes="true" runat="server"
                      Font-Size="XX-Small" OnNodeExpand="rtvTreeView_NodeExpand"
                      EnableDragAndDrop="True" EnableDragAndDropBetweenNodes="True"
                      OnNodeDrop="rtvTreeView_NodeDrop">
                      <CollapseAnimation Type="InQuint" Duration="100"></CollapseAnimation>
                      <ExpandAnimation Duration="100" Type="None"></ExpandAnimation>
                  </telerik:RadTreeView>
              </div>