diff --git a/dom/events/UIEvent.cpp b/dom/events/UIEvent.cpp
index eddebaf61673..7f6dd8689753 100644
--- a/dom/events/UIEvent.cpp
+++ b/dom/events/UIEvent.cpp
@@ -325,12 +325,6 @@ UIEvent::GetLayerY(int32_t* aLayerY)
   return NS_OK;
 }
 
-mozilla::dom::Event*
-UIEvent::AsEvent(void)
-{
-  return this;
-}
-
 NS_IMETHODIMP
 UIEvent::DuplicatePrivateData()
 {
diff --git a/dom/interfaces/events/nsIDOMUIEvent.idl b/dom/interfaces/events/nsIDOMUIEvent.idl
index 733c40df0c35..723d6cecabcb 100644
--- a/dom/interfaces/events/nsIDOMUIEvent.idl
+++ b/dom/interfaces/events/nsIDOMUIEvent.idl
@@ -45,6 +45,4 @@ interface nsIDOMUIEvent : nsISupports
   readonly attribute long               pageX;
   readonly attribute long               pageY;
   readonly attribute unsigned long      which;
-
-  [notxpcom, nostdcall] EventPtr AsEvent();
 };
diff --git a/dom/xbl/nsXBLPrototypeHandler.cpp b/dom/xbl/nsXBLPrototypeHandler.cpp
index aa6c01a8094c..5617c7eeaccd 100644
--- a/dom/xbl/nsXBLPrototypeHandler.cpp
+++ b/dom/xbl/nsXBLPrototypeHandler.cpp
@@ -1023,10 +1023,10 @@ nsXBLPrototypeHandler::ReportKeyConflict(const char16_t* aKey, const char16_t* a
 
 bool
 nsXBLPrototypeHandler::ModifiersMatchMask(
-                         nsIDOMUIEvent* aEvent,
+                         UIEvent* aEvent,
                          const IgnoreModifierState& aIgnoreModifierState)
 {
-  WidgetInputEvent* inputEvent = aEvent->AsEvent()->WidgetEventPtr()->AsInputEvent();
+  WidgetInputEvent* inputEvent = aEvent->WidgetEventPtr()->AsInputEvent();
   NS_ENSURE_TRUE(inputEvent, false);
 
   if (mKeyMask & cMetaMask) {
diff --git a/dom/xbl/nsXBLPrototypeHandler.h b/dom/xbl/nsXBLPrototypeHandler.h
index 9208bedcd8e0..6aa9d73192ef 100644
--- a/dom/xbl/nsXBLPrototypeHandler.h
+++ b/dom/xbl/nsXBLPrototypeHandler.h
@@ -21,7 +21,6 @@
 
 class nsIDOMEvent;
 class nsIContent;
-class nsIDOMUIEvent;
 class nsIObjectInputStream;
 class nsIObjectOutputStream;
 class nsXBLPrototypeBinding;
@@ -35,6 +34,7 @@ class AutoJSAPI;
 class EventTarget;
 class KeyboardEvent;
 class MouseEvent;
+class UIEvent;
 } // namespace dom
 
 namespace layers {
@@ -192,7 +192,7 @@ protected:
 
   void ReportKeyConflict(const char16_t* aKey, const char16_t* aModifiers, mozilla::dom::Element* aElement, const char *aMessageName);
   void GetEventType(nsAString& type);
-  bool ModifiersMatchMask(nsIDOMUIEvent* aEvent,
+  bool ModifiersMatchMask(mozilla::dom::UIEvent* aEvent,
                           const IgnoreModifierState& aIgnoreModifierState);
   nsresult DispatchXBLCommand(mozilla::dom::EventTarget* aTarget, nsIDOMEvent* aEvent);
   nsresult DispatchXULKeyCommand(nsIDOMEvent* aEvent);
diff --git a/editor/libeditor/EditorEventListener.cpp b/editor/libeditor/EditorEventListener.cpp
index 9c00b7061689..3bc7b86d90d7 100644
--- a/editor/libeditor/EditorEventListener.cpp
+++ b/editor/libeditor/EditorEventListener.cpp
@@ -455,7 +455,7 @@ EditorEventListener::HandleEvent(nsIDOMEvent* aEvent)
       // editor shouldn't handle this click event.
       if (mMouseDownOrUpConsumedByIME) {
         mMouseDownOrUpConsumedByIME = false;
-        mouseEvent->AsEvent()->PreventDefault();
+        mouseEvent->PreventDefault();
         return NS_OK;
       }
       return MouseClick(mouseEvent);
diff --git a/layout/xul/nsSplitterFrame.cpp b/layout/xul/nsSplitterFrame.cpp
index 2e8d63d3e4c4..4eb826befeaa 100644
--- a/layout/xul/nsSplitterFrame.cpp
+++ b/layout/xul/nsSplitterFrame.cpp
@@ -744,7 +744,7 @@ nsSplitterFrameInner::MouseDown(nsIDOMEvent* aMouseEvent)
      mChildInfosAfterCount = 0;
 
   int32_t c;
-  nsPoint pt = nsLayoutUtils::GetDOMEventCoordinatesRelativeTo(mouseEvent->AsEvent(),
+  nsPoint pt = nsLayoutUtils::GetDOMEventCoordinatesRelativeTo(mouseEvent,
                                                                mParentBox);
   if (isHorizontal) {
      c = pt.x;
diff --git a/layout/xul/nsXULPopupManager.cpp b/layout/xul/nsXULPopupManager.cpp
index f52220394e31..7ab8d580757f 100644
--- a/layout/xul/nsXULPopupManager.cpp
+++ b/layout/xul/nsXULPopupManager.cpp
@@ -2731,7 +2731,7 @@ nsXULPopupManager::KeyDown(KeyboardEvent* aKeyEvent)
     }
   }
 
-  aKeyEvent->AsEvent()->StopCrossProcessForwarding();
+  aKeyEvent->StopCrossProcessForwarding();
   return NS_OK;
 }