Index: src/main/java/org/apache/jackrabbit/core/xml/NamespaceContext.java
===================================================================
--- src/main/java/org/apache/jackrabbit/core/xml/NamespaceContext.java	(revision 664480)
+++ src/main/java/org/apache/jackrabbit/core/xml/NamespaceContext.java	(working copy)
@@ -108,13 +108,14 @@
      * @throws NamespaceException if the URI is not mapped
      */
     public String getPrefix(String uri) throws NamespaceException {
-        String prefix = (String) uriToPrefix.get(uri);
-        if (prefix != null) {
-            return prefix;
-        } else if (parent != null) {
-            return parent.getPrefix(uri);
-        } else {
-            throw new NamespaceException("Unknown URI: " + uri);
-        }
+	NamespaceContext current = this;
+	while (current != null) {
+	    String prefix = (String) current.uriToPrefix.get(uri);
+	    if (prefix != null) {
+	        return prefix;
+	    }
+	    current = current.parent;
+	}
+        throw new NamespaceException("Unknown URI: " + uri);
     }
 }