xpath: which is right?

[Suzan Foster <su@islief.nl>]

Taking the following XML:

  <foo>
     <bar id="1" />
     <bar id="2" />
     <bar id="3" />
     <fu />
   </foo>

which value should be returned by the xpath:

preceding::bar[1]/@id

libxslt says 3, whilst XML::XPath says 1.

groetjes, su.