XPath local-name not working in item_selector

I need to parse an XML-document. The following does work:

item_selector: '/publication-template:GetResponse/core:result/core:content'

print_r($this->elementsToMatch);

Returns the following:

(
    [0] => publication-template:GetResponse
    [1] => core:result
    [2] => core:content
)

This one does not work with the module, but with standard xPath:
/*[local-name()="GetResponse"]/*[local-name()="result"]/*[local-name()="content"]

print_r($this->elementsToMatch);
Returns the following:

(
    [0] => *
)

And no elements are imported this time.