Hi all: moving from 3.6.2 to 3.6.3 introduces an XML Schema validation error. Test case: XML document: https://github.com/geopython/pycsw/blob/master/tests/suites/default/post/Get... Associated XML Schema: http://schemas.opengis.net/csw/2.0.2/CSW-discovery.xsd (note there are numerous includes/imports. Full schema tree can be downloaded from http://schemas.opengis.net/SCHEMAS_OPENGIS_NET.zip). Code snippet: schema = etree.XMLSchema(file='/path/to/csw/2.0.2/CSW-discovery.xsd') parser = etree.XMLParser(schema=schema, resolve_entities=False) doc = etree.fromstring(postdata, parser) Result: Element '{http://www.opengis.net/cat/csw/2.0.2}GetRecordById', attribute 'service': The value '(null)' does not match the fixed value constraint 'CSW'. Testing results summary [1]: - lxml 3.6.1 && libxml2 2.9.1 passes - lxml 3.6.2 && libxml2 2.9.1 passes - lxml 3.6.3 && libxml2 2.9.4 FAILS with said validation error - lxml 3.6.4 && libxml2 2.9.4 FAILS with said validation error Any ideas? Is this a libxml2 issue? I notice 3.6.2 uses libxml2 2.9.1 whereas 3.6.3 uses libxml2 2.9.4 (on travis, fwiw). Let me know if you need more info or a clearer test case, or if/where I should file an issue. Thanks ..Tom [1] https://github.com/geopython/pycsw/pull/453