gst-metadata breaks on special filenames sometimes

While not using tagpy, but gst only for the metadata getting, I got this traceback:

Problem in gst_metadata:
Twisted traceback:
Traceback (most recent call last):
  File "threading.py", line 440, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.5/site-packages/twisted/python/threadpool.py", line 148, in _worker
    context.call(ctx, function, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/twisted/python/context.py", line 59, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python2.5/site-packages/twisted/python/context.py", line 37, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "/usr/lib/python2.5/site-packages/twisted/internet/threads.py", line 25, in _putResultInDeferred
    result = f(*args, **kwargs)
  File "/opt/elisa/elisa/plugins/base/metadata_providers/gst_metadata.py", line 241, in _get_metadata
    tags = self._get_tags(dict['uri'])
  File "/opt/elisa/elisa/plugins/base/metadata_providers/gst_metadata.py", line 121, in _get_tags
    source.set_property('location', filename)
exceptions.TypeError: could not convert argument to correct param type