Strangeness with request.getHeader("User-Agent")

[Jann VanOver]

I can use request.getHeader() in my JSP scriptlet (Tomcat 3.2.1) and it
works just fine:

<% String myUserAgent = request.getHeader("User-Agent"); %>
User-Agent = <%= myUserAgent %><br>
<jsp:setProperty
        name="userAgent" 
        property="userAgent" 
        value="<%= myUserAgent %>"   /> 

But when I try to use it directly in a jsp:setProperty statement, I get an
error:

<jsp:setProperty
        name="userAgent" 
        property="userAgent" 
        value="<%= request.getHeader("User-Agent") %>"   /> 
 
... Attribute User-Agent has no value

Any idea why?