diff --git a/xpcom/build/nsXPComInit.cpp b/xpcom/build/nsXPComInit.cpp
index 7e387138c780..80239b529d9e 100644
--- a/xpcom/build/nsXPComInit.cpp
+++ b/xpcom/build/nsXPComInit.cpp
@@ -199,7 +199,6 @@ NS_GENERIC_FACTORY_CONSTRUCTOR(nsSupportsDoubleImpl)
 NS_GENERIC_FACTORY_CONSTRUCTOR(nsSupportsVoidImpl)
 NS_GENERIC_FACTORY_CONSTRUCTOR(nsSupportsInterfacePointerImpl)
 
-NS_GENERIC_FACTORY_CONSTRUCTOR(nsArray)
 NS_GENERIC_FACTORY_CONSTRUCTOR_INIT(nsConsoleService, Init)
 NS_DECL_CLASSINFO(nsConsoleService)
 NS_GENERIC_FACTORY_CONSTRUCTOR(nsAtomService)
diff --git a/xpcom/ds/nsArray.cpp b/xpcom/ds/nsArray.cpp
index 6f14b6b65a6c..7da90f3b101d 100644
--- a/xpcom/ds/nsArray.cpp
+++ b/xpcom/ds/nsArray.cpp
@@ -39,6 +39,7 @@
 #include "nsArray.h"
 #include "nsArrayEnumerator.h"
 #include "nsWeakReference.h"
+#include "nsThreadUtils.h"
 
 // used by IndexOf()
 struct findIndexOfClosure
@@ -50,7 +51,13 @@ struct findIndexOfClosure
 
 static PRBool FindElementCallback(void* aElement, void* aClosure);
 
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsArray)
+NS_INTERFACE_MAP_BEGIN(nsArray)
+  NS_INTERFACE_MAP_ENTRY(nsIArray)
+  NS_INTERFACE_MAP_ENTRY(nsIMutableArray)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIMutableArray)
+NS_INTERFACE_MAP_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsArrayCC)
   NS_INTERFACE_MAP_ENTRY(nsIArray)
   NS_INTERFACE_MAP_ENTRY(nsIMutableArray)
   NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIMutableArray)
@@ -61,14 +68,18 @@ nsArray::~nsArray()
     Clear();
 }
 
-NS_IMPL_CYCLE_COLLECTING_ADDREF(nsArray)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(nsArray)
 
-NS_IMPL_CYCLE_COLLECTION_CLASS(nsArray)
-NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsArray)
+NS_IMPL_ADDREF(nsArray)
+NS_IMPL_RELEASE(nsArray)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsArrayCC)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsArrayCC)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsArrayCC)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsArrayCC)
     tmp->Clear();
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsArray)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsArrayCC)
     NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSCOMARRAY(mArray)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
@@ -215,3 +226,14 @@ FindElementCallback(void *aElement, void* aClosure)
 
     return PR_TRUE;
 }
+
+NS_METHOD nsArrayConstructor(nsISupports *aOuter, const nsIID& aIID, void **aResult) {
+    if (aOuter)
+        return NS_ERROR_NO_AGGREGATION;
+
+    nsCOMPtr<nsIArray> inst = NS_IsMainThread() ? new nsArrayCC : new nsArray;
+    if (!inst)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    return inst->QueryInterface(aIID, aResult); 
+}
diff --git a/xpcom/ds/nsArray.h b/xpcom/ds/nsArray.h
index 7f59888eb70d..2805a8e5bbc4 100644
--- a/xpcom/ds/nsArray.h
+++ b/xpcom/ds/nsArray.h
@@ -64,15 +64,27 @@ public:
     nsArray(const nsCOMArray_base& aBaseArray) : mArray(aBaseArray)
     { }
     
-    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-    NS_DECL_CYCLE_COLLECTION_CLASS(nsArray)
+    NS_DECL_ISUPPORTS
     NS_DECL_NSIARRAY
     NS_DECL_NSIMUTABLEARRAY
 
-private:
+protected:
     ~nsArray();
 
     nsCOMArray_base mArray;
 };
 
+class nsArrayCC : public nsArray
+{
+public:
+    nsArrayCC() : nsArray() { }
+    nsArrayCC(const nsCOMArray_base& aBaseArray) : nsArray(aBaseArray)
+    { }
+    
+    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+    NS_DECL_CYCLE_COLLECTION_CLASS(nsArrayCC)
+};
+
+NS_METHOD nsArrayConstructor(nsISupports *aOuter, const nsIID& aIID, void **aResult);
+
 #endif