--- lxml-3.0.2/src/lxml/parser.pxi	2012-10-07 20:04:15.000000000 +0200
+++ lxml-3.0.2-changed/src/lxml/parser.pxi	2013-01-11 10:23:36.448599278 +0100
@@ -500,7 +500,7 @@
     def __dealloc__(self):
         if self._validator is not None:
             self._validator.disconnect()
-        if self._lock is not NULL:
+        if config.ENABLE_THREADING and self._lock is not NULL:
             python.PyThread_free_lock(self._lock)
         if self._c_ctxt is not NULL:
             xmlparser.xmlFreeParserCtxt(self._c_ctxt)