diff --git a/python/tests/thread2.py b/python/tests/thread2.py
index f7d2595b..9991b4ce 100755
--- a/python/tests/thread2.py
+++ b/python/tests/thread2.py
@@ -96,6 +96,9 @@ if failed:
 
 # Memory debug specific
 libxml2.cleanupParser()
+# Note that this can leak memory on Windows if the global state
+# destructors weren't run yet. They should be called eventually,
+# so this leak should be harmless.
 if libxml2.debugMemory(1) == 0:
     print("OK")
 else:
diff --git a/xmlmemory.c b/xmlmemory.c
index 3b1ebaf0..1e999b11 100644
--- a/xmlmemory.c
+++ b/xmlmemory.c
@@ -878,7 +878,16 @@ xmlCleanupMemory(void) {
  */
 void
 xmlCleanupMemoryInternal(void) {
+    /*
+     * Don't clean up mutex on Windows. Global state destructors can call
+     * malloc functions after xmlCleanupParser was called. If memory
+     * debugging is enabled, xmlMemMutex can be used after cleanup.
+     *
+     * See python/tests/thread2.py
+     */
+#if !defined(LIBXML_THREAD_ENABLED) || !defined(_WIN32)
     xmlCleanupMutex(&xmlMemMutex);
+#endif
 }
 
 /**