diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java
index 9d2e2b65a..484f17da0 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java
@@ -22,13 +22,12 @@ import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.openjpa.enhance.PersistenceCapable;
 import org.apache.openjpa.enhance.Reflection;
@@ -87,7 +86,7 @@ public class ClassMapping
     private ClassMapping[] _assignMaps = null;
 
     // maps columns to joinables
-    private final Map _joinables = Collections.synchronizedMap(new HashMap());
+    private final Map _joinables = new ConcurrentHashMap();
 
     /**
      * Constructor. Supply described type and owning repository.