s:url & s:param does not work on struts 2.3.15.1

[Omar Ngarigari]

Hello,

I am in the process of upgrading my struts2.3.1.2 application to 
struts2.3.15.1. Everything works fine except the <s:url> and <s:param> tags.

In struts2.3.1.2, I have the following code in jsp file
<s:url var "add" action="addState">
          <s:param name="state.name">%{stateName}</s:param>
</s:url>
<s:a href="%{add}">Add</s:a>

I used to get correct state name when using struts2.3.1.2. However, using 
struts2.3.15.1, I am getting the following on web-browser page: %{stateName}


Thanks,

Omar N.