setHeader("FOO", xpath("/foo/bar/@value")) is of type net.sf.saxon.dom.DOMNodeList - not String, ideas?

[Chris]

If my in msg body is:
<foo>
  <bar value="hello"/>
</foo>

...then, when doing:

.setHeader("FOO", xpath("/foo/bar/@value"))

I expect the header named "FOO" to have String value of "hello", 
instead, I see: net.sf.saxon.dom.DOMNodeList@74184b3b

Is there any way to make this work?

Thanks,

Chris