diff --git a/dom/events/DataTransferItem.cpp b/dom/events/DataTransferItem.cpp
index 0cf53e83a36f..aea429a6810e 100644
--- a/dom/events/DataTransferItem.cpp
+++ b/dom/events/DataTransferItem.cpp
@@ -326,10 +326,9 @@ DataTransferItem::GetAsEntry(nsIPrincipal& aSubjectPrincipal,
   if (target) {
     global = target->GetOwnerGlobal();
   } else {
-    nsCOMPtr<nsIDOMEvent> event =
-      do_QueryInterface(mDataTransfer->GetParentObject());
+    RefPtr<Event> event = do_QueryObject(mDataTransfer->GetParentObject());
     if (event) {
-      global = event->InternalDOMEvent()->GetParentObject();
+      global = event->GetParentObject();
     }
   }
 
@@ -469,8 +468,8 @@ DataTransferItem::GetAsString(FunctionStringCallback* aCallback,
   if (parent && !global) {
     if (nsCOMPtr<dom::EventTarget> target = do_QueryInterface(parent)) {
       global = target->GetOwnerGlobal();
-    } else if (nsCOMPtr<nsIDOMEvent> event = do_QueryInterface(parent)) {
-      global = event->InternalDOMEvent()->GetParentObject();
+    } else if (RefPtr<Event> event = do_QueryObject(parent)) {
+      global = event->GetParentObject();
     }
   }
   if (global) {
diff --git a/dom/events/Event.cpp b/dom/events/Event.cpp
index fa33dcc3ab43..96ef83e85511 100644
--- a/dom/events/Event.cpp
+++ b/dom/events/Event.cpp
@@ -137,6 +137,7 @@ Event::~Event()
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Event)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
   NS_INTERFACE_MAP_ENTRY(nsISupports)
+  NS_INTERFACE_MAP_ENTRY(Event)
   NS_INTERFACE_MAP_ENTRY(nsIDOMEvent)
 NS_INTERFACE_MAP_END
 
diff --git a/dom/events/Event.h b/dom/events/Event.h
index 1a267e409cd1..cfcf8a639387 100755
--- a/dom/events/Event.h
+++ b/dom/events/Event.h
@@ -46,10 +46,17 @@ class XULCommandEvent;
 #include "mozilla/dom/GeneratedEventList.h"
 #undef GENERATED_EVENT
 
+// IID for Event
+#define NS_EVENT_IID                                            \
+  { 0x71139716, 0x4d91, 0x4dee,                                 \
+      { 0xba, 0xf9, 0xe3, 0x3b, 0x80, 0xc1, 0x61, 0x61 } }
+
 class Event : public nsIDOMEvent,
               public nsWrapperCache
 {
 public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_EVENT_IID)
+
   Event(EventTarget* aOwner,
         nsPresContext* aPresContext,
         WidgetEvent* aEvent);
@@ -393,6 +400,8 @@ private:
   bool mOriginalWantsPopupControlCheck;
 };
 
+NS_DEFINE_STATIC_IID_ACCESSOR(Event, NS_EVENT_IID)
+
 } // namespace dom
 } // namespace mozilla