diff -r 92932cd370a4 -r c3c3d1318130 xmlclass/xsdschema.py
--- a/xmlclass/xsdschema.py	Tue Aug 15 16:48:49 2017 +0300
+++ b/xmlclass/xsdschema.py	Tue Aug 15 17:01:51 2017 +0300
@@ -992,7 +992,7 @@
             return False
         for name, value in schema.items():
             ref_value = reference.get(name, None)
-            if ref_value is None and value != None:
+            if ref_value is None and value is not None:
                 return False
             result = CompareSchema(value, ref_value)
             if not result: