diff --git a/components/script/dom/webidls/MouseEvent.webidl b/components/script/dom/webidls/MouseEvent.webidl
index c95739429a8..e9f7a31db48 100644
--- a/components/script/dom/webidls/MouseEvent.webidl
+++ b/components/script/dom/webidls/MouseEvent.webidl
@@ -3,7 +3,8 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-mouseevent
-[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict)]
+[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict),
+ Exposed=Window]
 interface MouseEvent : UIEvent {
     readonly    attribute long           screenX;
     readonly    attribute long           screenY;