diff --git a/mozilla/extensions/java/xpcom/src/nsJavaWrapper.cpp b/mozilla/extensions/java/xpcom/src/nsJavaWrapper.cpp
index c9426003608..0113ea0cd39 100644
--- a/mozilla/extensions/java/xpcom/src/nsJavaWrapper.cpp
+++ b/mozilla/extensions/java/xpcom/src/nsJavaWrapper.cpp
@@ -1519,9 +1519,17 @@ JAVAPROXY_NATIVE(callXPCOMMethod) (JNIEnv *env, jclass that, jobject aJavaProxy,
   }
 
   // Call the XPCOM method
-  nsresult invokeResult;
-  invokeResult = XPTC_InvokeByIndex(inst->GetInstance(), methodIndex,
-                                    paramCount, params);
+  const nsIID* iid;
+  iinfo->GetIIDShared(&iid);
+  nsISupports* realObject;
+  rv = inst->GetInstance()->QueryInterface(*iid, (void**) &realObject);
+  if (NS_FAILED(rv)) {
+    ThrowException(env, rv, "Failed to get real XPCOM object");
+    return nsnull;
+  }
+  nsresult invokeResult = XPTC_InvokeByIndex(realObject, methodIndex,
+                                             paramCount, params);
+  NS_RELEASE(realObject);
 
   // Clean up params
   jobject result = nsnull;
@@ -1756,3 +1764,26 @@ JAVAPROXY_NATIVE(finalizeProxy) (JNIEnv *env, jclass that, jobject aJavaProxy)
 #endif
 }
 
+/**
+ *  org.mozilla.xpcom.XPCOMJavaProxy.isSameXPCOMObject
+ */
+extern "C" NS_EXPORT jboolean
+JAVAPROXY_NATIVE(isSameXPCOMObject) (JNIEnv *env, jclass that,
+                                     jobject aProxy1, jobject aProxy2)
+{
+  void* xpcom_obj1;
+  nsresult rv = GetXPCOMInstFromProxy(env, aProxy1, &xpcom_obj1);
+  if (NS_SUCCEEDED(rv)) {
+    void* xpcom_obj2;
+    rv = GetXPCOMInstFromProxy(env, aProxy2, &xpcom_obj2);
+    if (NS_SUCCEEDED(rv)) {
+      JavaXPCOMInstance* inst1 = NS_STATIC_CAST(JavaXPCOMInstance*, xpcom_obj1);
+      JavaXPCOMInstance* inst2 = NS_STATIC_CAST(JavaXPCOMInstance*, xpcom_obj2);
+      if (inst1->GetInstance() == inst2->GetInstance()) {
+        return JNI_TRUE;
+      }
+    }
+  }
+  return JNI_FALSE;
+}
+
diff --git a/mozilla/extensions/java/xpcom/src/nsJavaXPCOMBindingUtils.cpp b/mozilla/extensions/java/xpcom/src/nsJavaXPCOMBindingUtils.cpp
index 75797c7adc1..c04dfa4de71 100644
--- a/mozilla/extensions/java/xpcom/src/nsJavaXPCOMBindingUtils.cpp
+++ b/mozilla/extensions/java/xpcom/src/nsJavaXPCOMBindingUtils.cpp
@@ -721,24 +721,27 @@ GetNewOrUsedJavaObject(JNIEnv* env, nsISupports* aXPCOMObject,
     return NS_OK;
   }
 
+  // Get the root nsISupports of the xpcom object
+  nsCOMPtr<nsISupports> rootObject = do_QueryInterface(aXPCOMObject, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
   // Get associated Java object from hash table
-  rv = gNativeToJavaProxyMap->Find(env, aXPCOMObject, aIID, aResult);
-  if (NS_FAILED(rv))
-    return rv;
+  rv = gNativeToJavaProxyMap->Find(env, rootObject, aIID, aResult);
+  NS_ENSURE_SUCCESS(rv, rv);
   if (*aResult)
     return NS_OK;
 
   // No Java object is associated with the given XPCOM object, so we
   // create a Java proxy.
-  return CreateJavaProxy(env, aXPCOMObject, aIID, aResult);
+  return CreateJavaProxy(env, rootObject, aIID, aResult);
 }
 
 nsresult
 GetNewOrUsedXPCOMObject(JNIEnv* env, jobject aJavaObject, const nsIID& aIID,
                         nsISupports** aResult, PRBool* aIsXPTCStub)
 {
-  NS_PRECONDITION(aResult != nsnull && aIsXPTCStub != nsnull, "null ptr");
-  if (!aResult || !aIsXPTCStub)
+  NS_PRECONDITION(aResult != nsnull, "null ptr");
+  if (!aResult)
     return NS_ERROR_NULL_POINTER;
 
   nsresult rv;
@@ -757,23 +760,28 @@ GetNewOrUsedXPCOMObject(JNIEnv* env, jobject aJavaObject, const nsIID& aIID,
   if (isProxy) {
     void* inst;
     rv = GetXPCOMInstFromProxy(env, aJavaObject, &inst);
-    if (NS_SUCCEEDED(rv)) {
-      *aResult = NS_STATIC_CAST(JavaXPCOMInstance*, inst)->GetInstance();
-      NS_ADDREF(*aResult);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsISupports* rootObject =
+              NS_STATIC_CAST(JavaXPCOMInstance*, inst)->GetInstance();
+    rv = rootObject->QueryInterface(aIID, (void**) aResult);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (aIsXPTCStub) {
       *aIsXPTCStub = PR_FALSE;
-      return NS_OK;
     }
+    return NS_OK;
   }
 
-  *aIsXPTCStub = PR_TRUE;
+  if (aIsXPTCStub) {
+    *aIsXPTCStub = PR_TRUE;
+  }
 
   nsJavaXPTCStub* stub;
   rv = gJavaToXPTCStubMap->Find(env, aJavaObject, aIID, &stub);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
+  NS_ENSURE_SUCCESS(rv, rv);
   if (stub) {
-    // stub is already AddRef'd
+    // stub is already AddRef'd and QI'd
     *aResult = NS_STATIC_CAST(nsISupports*,
                               NS_STATIC_CAST(nsXPTCStubBase*, stub));
     return NS_OK;
@@ -791,8 +799,7 @@ GetNewOrUsedXPCOMObject(JNIEnv* env, jobject aJavaObject, const nsIID& aIID,
 
   nsCOMPtr<nsIInterfaceInfo> iinfo;
   rv = iim->GetInfoForIID(&aIID, getter_AddRefs(iinfo));
-  if (NS_FAILED(rv))
-    return rv;
+  NS_ENSURE_SUCCESS(rv, rv);
 
   // Create XPCOM stub
   stub = new nsJavaXPTCStub(aJavaObject, iinfo);