AttributeError: Element instance has no attribute 'matchesNode'

[a1s]

I get the following error when xhtml2pdf is run with debug option:

Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\sx\pisa3\pisa_parser.py", line 231, in CSSCollect
cssAttrMap[cssAttrName] = node.getCSSAttr(c.cssCascade, cssAttrName)
  File "C:\Python27\lib\site-packages\sx\pisa3\pisa_parser.py", line 195, in getCSSAttr
result = cssCascade.findStyleFor(self.cssElement, attrName, default)
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 133, in findStyleFor
rule = self.findCSSRulesFor(element, attrName)
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 153, in findCSSRulesFor
rules += ruleset.findCSSRuleFor(element, attrName)
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 504, in findCSSRuleFor
return self.findCSSRulesFor(*args, **kw)[-1:]
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 496, in findCSSRulesFor
if (attrName in declarations) and (nodeFilter.matches(element)):
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 272, in matches
if not qualifier.matches(element):
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 463, in matches
return selector.matches(element.getPreviousSibling())
  File "C:\Python27\lib\site-packages\sx\w3c\css.py", line 268, in matches
if not element.matchesNode(self.fullName):
AttributeError: Element instance has no attribute 'matchesNode'

should CSSDOMElementInterface.getPreviousSibling() return a CSSElementInterfaceAbstract instance, or should CSSSelectorBase.matches() accept unwrapped DOM elements?