jaxen

According the documentation of BaseXPath.selectNodes,
"nodes will be returned in document-order" unless I'm
"using XPath expressions involving the union operator".
But it seems that //somthing expressions return the result
not in document order. E.g for this XML:

<a>
<x>1</x>
<b>
<x>2</x>
<x>3</x>
</b>
<x>4</x>
</a>

XPath expression //x will return the nodes in order 1, 4,
2, 3.

I have tried it with both 1.0 FCS and the 1.1 beta.