Declaring Variables Inline - <os:Var> does not work

Declaring Variables Inline - <os:Var> does not work. Following is a simple gadget using os:Var.
The gadget default view should show "This value of myvar is 3". But actaully is shows "This value of myvar is".

<Module>
<ModulePrefs title="Varible Replacement Templating Example" height="400" width="400">
<Require feature="opensocial-templates">
</Require>
</ModulePrefs>
<Content view="default" type="html">
<![CDATA[
<div>
<script type="text/os-template">
<os:Var key="myvar" value="3">This value of myvar is ${myvar}</os:Var>
</script>
</div>
]]>
</Content>
</Module>