diff --git a/src/calibre/utils/xml_parse.py b/src/calibre/utils/xml_parse.py
index a82d4bc773..d0228d5e3f 100644
--- a/src/calibre/utils/xml_parse.py
+++ b/src/calibre/utils/xml_parse.py
@@ -6,14 +6,29 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 
 
 from lxml import etree
+import threading
+
 
 # resolve_entities is turned off as entities can cause
 # reads of local files, for example:
 # <!DOCTYPE foo [ <!ENTITY passwd SYSTEM "file:///etc/passwd" >]>
-SAFE_XML_PARSER = etree.XMLParser(recover=True, no_network=True, resolve_entities=False)
-SAFE_XML_PARSER_NO_RECOVER = etree.XMLParser(recover=False, no_network=True, resolve_entities=False)
+
+
+class GlobalParserTLS(threading.local):
+
+    def __call__(self, recover):
+        parsers = getattr(self, 'parsers', None)
+        if parsers is None:
+            self.parsers = parsers = {
+                True: etree.XMLParser(recover=True, no_network=True, resolve_entities=False),
+                False: etree.XMLParser(recover=False, no_network=True, resolve_entities=False)
+            }
+        return parsers[recover]
+
+
+_global_tls = GlobalParserTLS()
 fs = etree.fromstring
 
 
 def safe_xml_fromstring(string_or_bytes, recover=True):
-    return fs(string_or_bytes, SAFE_XML_PARSER if recover else SAFE_XML_PARSER_NO_RECOVER)
+    return fs(string_or_bytes, _global_tls(recover))