gistfile1.diff

diff --git a/src/org/ringojs/wrappers/Storable.java b/src/org/ringojs/wrappers/Storable.java
index 2ee3055..302fa40 100644
--- a/src/org/ringojs/wrappers/Storable.java
+++ b/src/org/ringojs/wrappers/Storable.java
@@ -70,7 +70,7 @@ public class Storable extends ScriptableObject {
     }
 
     @JSStaticFunction
-    public static Scriptable defineClass(Scriptable store, String type)
+    public static Scriptable defineClass(Scriptable store, String type, Object mapping)
             throws NoSuchMethodException {
         int attr = DONTENUM | PERMANENT | READONLY;
         Scriptable scope = ScriptRuntime.getTopCallScope(Context.getCurrentContext());
@@ -80,6 +80,9 @@ public class Storable extends ScriptableObject {
         // create the constructor, visible to the application
         BaseFunction ctor = new FactoryFunction(prototype, scope, FactoryType.CONSTRUCTOR);
         ctor.setImmunePrototypeProperty(prototype);
+        if (mapping != Undefined.instance) {
+            ctor.defineProperty("mapping", mapping, attr);
+        }
         prototype.setParentScope(ctor);
         defineProperty(prototype, "constructor", ctor, attr);
         // create the factory function, visible to the store implementation