diff --git a/components/script/dom/event.rs b/components/script/dom/event.rs
index 43250102b5d..77f7f7aa595 100644
--- a/components/script/dom/event.rs
+++ b/components/script/dom/event.rs
@@ -10,6 +10,7 @@ use dom::bindings::global::GlobalRef;
 use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::utils::{Reflector, reflect_dom_object};
 use dom::eventtarget::{EventTarget, EventTargetHelpers};
+use dom::uievent::{UIEventTypeId};
 use util::str::DOMString;
 
 use std::borrow::ToOwned;
@@ -32,12 +33,10 @@ pub enum EventPhase {
 pub enum EventTypeId {
     CustomEvent,
     HTMLEvent,
-    KeyboardEvent,
     MessageEvent,
-    MouseEvent,
     ProgressEvent,
     StorageEvent,
-    UIEvent,
+    UIEvent(UIEventTypeId),
     ErrorEvent,
     CloseEvent
 }
diff --git a/components/script/dom/keyboardevent.rs b/components/script/dom/keyboardevent.rs
index ff41ad9ca3c..1dbbcb97a2b 100644
--- a/components/script/dom/keyboardevent.rs
+++ b/components/script/dom/keyboardevent.rs
@@ -11,7 +11,7 @@ use dom::bindings::global::GlobalRef;
 use dom::bindings::js::{Root, RootedReference};
 use dom::bindings::utils::{Reflectable, reflect_dom_object};
 use dom::event::{Event, EventTypeId};
-use dom::uievent::UIEvent;
+use dom::uievent::{UIEvent, UIEventTypeId};
 use dom::window::Window;
 use msg::constellation_msg;
 use msg::constellation_msg::{Key, KeyModifiers};
@@ -43,14 +43,14 @@ pub struct KeyboardEvent {
 
 impl KeyboardEventDerived for Event {
     fn is_keyboardevent(&self) -> bool {
-        *self.type_id() == EventTypeId::KeyboardEvent
+        *self.type_id() == EventTypeId::UIEvent(UIEventTypeId::KeyboardEvent)
     }
 }
 
 impl KeyboardEvent {
     fn new_inherited() -> KeyboardEvent {
         KeyboardEvent {
-            uievent: UIEvent::new_inherited(EventTypeId::KeyboardEvent),
+            uievent: UIEvent::new_inherited(UIEventTypeId::KeyboardEvent),
             key: Cell::new(None),
             key_string: RefCell::new("".to_owned()),
             code: RefCell::new("".to_owned()),
diff --git a/components/script/dom/mouseevent.rs b/components/script/dom/mouseevent.rs
index a160d7a6c1f..0a15c8ad640 100644
--- a/components/script/dom/mouseevent.rs
+++ b/components/script/dom/mouseevent.rs
@@ -12,7 +12,7 @@ use dom::bindings::js::{JS, MutNullableHeap, Root, RootedReference};
 use dom::bindings::utils::reflect_dom_object;
 use dom::event::{Event, EventTypeId, EventBubbles, EventCancelable};
 use dom::eventtarget::EventTarget;
-use dom::uievent::UIEvent;
+use dom::uievent::{UIEvent, UIEventTypeId};
 use dom::window::Window;
 use util::opts;
 use util::str::DOMString;
@@ -37,14 +37,14 @@ pub struct MouseEvent {
 
 impl MouseEventDerived for Event {
     fn is_mouseevent(&self) -> bool {
-        *self.type_id() == EventTypeId::MouseEvent
+        *self.type_id() == EventTypeId::UIEvent(UIEventTypeId::MouseEvent)
     }
 }
 
 impl MouseEvent {
     fn new_inherited() -> MouseEvent {
         MouseEvent {
-            uievent: UIEvent::new_inherited(EventTypeId::MouseEvent),
+            uievent: UIEvent::new_inherited(UIEventTypeId::MouseEvent),
             screen_x: Cell::new(0),
             screen_y: Cell::new(0),
             client_x: Cell::new(0),
diff --git a/components/script/dom/uievent.rs b/components/script/dom/uievent.rs
index 351a6d39443..b9d66082594 100644
--- a/components/script/dom/uievent.rs
+++ b/components/script/dom/uievent.rs
@@ -19,6 +19,13 @@ use util::str::DOMString;
 use std::cell::Cell;
 use std::default::Default;
 
+#[derive(JSTraceable, PartialEq, HeapSizeOf)]
+pub enum UIEventTypeId {
+    MouseEvent,
+    KeyboardEvent,
+    UIEvent,
+}
+
 // https://dvcs.w3.org/hg/dom3events/raw-file/tip/html/DOM3-Events.html#interface-UIEvent
 #[dom_struct]
 #[derive(HeapSizeOf)]
@@ -30,21 +37,24 @@ pub struct UIEvent {
 
 impl UIEventDerived for Event {
     fn is_uievent(&self) -> bool {
-        *self.type_id() == EventTypeId::UIEvent
+        match *self.type_id() {
+            EventTypeId::UIEvent(_) => true,
+            _ => false
+        }
     }
 }
 
 impl UIEvent {
-    pub fn new_inherited(type_id: EventTypeId) -> UIEvent {
+    pub fn new_inherited(type_id: UIEventTypeId) -> UIEvent {
         UIEvent {
-            event: Event::new_inherited(type_id),
+            event: Event::new_inherited(EventTypeId::UIEvent(type_id)),
             view: Default::default(),
             detail: Cell::new(0),
         }
     }
 
     pub fn new_uninitialized(window: &Window) -> Root<UIEvent> {
-        reflect_dom_object(box UIEvent::new_inherited(EventTypeId::UIEvent),
+        reflect_dom_object(box UIEvent::new_inherited(UIEventTypeId::UIEvent),
                            GlobalRef::Window(window),
                            UIEventBinding::Wrap)
     }