diff --git a/globals.c b/globals.c
index 811160f..9c1b1d2 100644
--- a/globals.c
+++ b/globals.c
@@ -46,8 +46,10 @@
 
 void xmlCleanupGlobals()
 {
-    if (xmlThrDefMutex != NULL)
+    if (xmlThrDefMutex != NULL) {
 	xmlFreeMutex(xmlThrDefMutex);
+	xmlThrDefMutex = NULL;
+    }
 }
 
 /************************************************************************