--- a/jdk/src/share/classes/jdk/internal/util/xml/PropertiesDefaultHandler.java	Mon Oct 21 10:54:46 2013 +0200
+++ b/jdk/src/share/classes/jdk/internal/util/xml/PropertiesDefaultHandler.java	Mon Oct 21 11:15:41 2013 +0200
@@ -27,6 +27,7 @@
 
 import java.io.*;
 import java.util.InvalidPropertiesFormatException;
+import java.util.Map.Entry;
 import java.util.Properties;
 import jdk.internal.org.xml.sax.Attributes;
 import jdk.internal.org.xml.sax.InputSource;
@@ -107,12 +108,17 @@
                 writer.writeEndElement();
             }
 
-            for (String key : props.stringPropertyNames()) {
-                String val = props.getProperty(key);
-                writer.writeStartElement(ELEMENT_ENTRY);
-                writer.writeAttribute(ATTR_KEY, key);
-                writer.writeCharacters(val);
-                writer.writeEndElement();
+            synchronized(props) {
+                for (Entry<Object, Object> e : props.entrySet()) {
+                    final Object k = e.getKey();
+                    final Object v = e.getValue();
+                    if (k instanceof String && v instanceof String) {
+                        writer.writeStartElement(ELEMENT_ENTRY);
+                        writer.writeAttribute(ATTR_KEY, (String)k);
+                        writer.writeCharacters((String)v);
+                        writer.writeEndElement();
+                    }
+                }
             }
 
             writer.writeEndElement();