diff --git a/src/main/java/org/dom4j/tree/QNameCache.java b/src/main/java/org/dom4j/tree/QNameCache.java
index d37e8aaa..ee856c3a 100644
--- a/src/main/java/org/dom4j/tree/QNameCache.java
+++ b/src/main/java/org/dom4j/tree/QNameCache.java
@@ -52,11 +52,15 @@ public QNameCache(DocumentFactory documentFactory) {
      */
     public List<QName> getQNames() {
         List<QName> answer = new ArrayList<QName>();
-        answer.addAll(noNamespaceCache.values());
+	synchronized(noNamespaceCache) {
+            answer.addAll(noNamespaceCache.values());
+	}
 
-        for (Map<String, QName> map : namespaceCache.values()) {
-            answer.addAll(map.values());
-        }
+	synchronized(namespaceCache) {
+            for (Map<String, QName> map : namespaceCache.values()) {
+                answer.addAll(map.values());
+            }
+	}
 
         return answer;
     }
@@ -297,4 +301,4 @@ protected QName createQName(String name, Namespace namespace,
  * POSSIBILITY OF SUCH DAMAGE.
  * 
  * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
- */
\ No newline at end of file
+ */