diff --git a/openjpa-lib/src/main/java/org/apache/openjpa/lib/conf/ConfigurationImpl.java b/openjpa-lib/src/main/java/org/apache/openjpa/lib/conf/ConfigurationImpl.java
index 8a0008b0b..09b3a967f 100644
--- a/openjpa-lib/src/main/java/org/apache/openjpa/lib/conf/ConfigurationImpl.java
+++ b/openjpa-lib/src/main/java/org/apache/openjpa/lib/conf/ConfigurationImpl.java
@@ -118,7 +118,7 @@ public class ConfigurationImpl
     private boolean _globals = false;
     private String _auto = null;
     private final List<Value> _vals = new ArrayList<Value>();
-    private Set<String> _supportedKeys;
+    private Set<String> _supportedKeys = new TreeSet<String>();
     
     // property listener helper
     private PropertyChangeSupport _changeSupport = null;
@@ -697,16 +697,16 @@ public class ConfigurationImpl
      * The Values that are {@linkplain Value#makePrivate() marked private} are filtered out. 
      */
     public Set<String> getPropertyKeys() {
-        if (_supportedKeys != null) 
-            return _supportedKeys;
-        
-        _supportedKeys = new TreeSet<String>();
-        for (Value val : _vals) {
-            if (val.isPrivate())
-                continue;
-            List<String> keys = val.getPropertyKeys();
-            for (String key : keys) {
-                _supportedKeys.add(fixPrefix(key));
+        synchronized (_supportedKeys) {
+            if (_supportedKeys.size() == 0) {
+                for (Value val : _vals) {
+                    if (val.isPrivate())
+                        continue;
+                    List<String> keys = val.getPropertyKeys();
+                    for (String key : keys) {
+                        _supportedKeys.add(fixPrefix(key));
+                    }
+                }
             }
         }
         return _supportedKeys;
diff --git a/openjpa-persistence-jdbc/src/test/java/org/apache/openjpa/conf/TestGetProperty.java b/openjpa-persistence-jdbc/src/test/java/org/apache/openjpa/conf/TestGetProperty.java
new file mode 100644
index 000000000..e0c698727
--- /dev/null
+++ b/openjpa-persistence-jdbc/src/test/java/org/apache/openjpa/conf/TestGetProperty.java
@@ -0,0 +1,75 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.openjpa.conf;
+
+import java.util.*;
+
+import javax.persistence.*;
+
+import junit.framework.*;
+
+import org.apache.openjpa.persistence.*;
+
+public class TestGetProperty extends TestCase {
+    private EntityManagerFactory emf;
+
+    public void setUp() throws Exception {
+        emf = (OpenJPAEntityManagerFactory) Persistence
+                .createEntityManagerFactory("test");
+    }
+
+    public void tearDown() throws Exception {
+        emf.close();
+        emf = null;
+    }
+
+    public void testGetProperty() {
+        try {
+            Collection<Thread> tests = new ArrayList<Thread>();
+            for (int i = 0; i < 10; i++) {
+                Test test = new Test();
+                test.start();
+                tests.add(test);
+            }
+
+            for (Thread test : tests)
+                test.join();
+        } catch (Exception e) {
+            e.printStackTrace();
+            fail(e.getMessage());
+        }
+    }
+
+    class Test extends Thread {
+        EntityManager em;
+
+        public Test() {
+            this.em = emf.createEntityManager();
+        }
+
+        @Override
+        public void run() {
+            for (int i = 0; i < 10; i++) {
+                em.getProperties();
+            }
+            if (em != null && em.isOpen())
+                em.close();
+        }
+    }
+}