diff --git a/ed/idl/portals.idl b/ed/idl/portals.idl
index 0957b2a9c4de..d0b1328897ea 100644
--- a/ed/idl/portals.idl
+++ b/ed/idl/portals.idl
@@ -43,8 +43,6 @@ dictionary PortalActivateEventInit : EventInit {
     any data = null;
 };
 
-typedef (WindowProxy or MessagePort or ServiceWorker or HTMLPortalElement or PortalHost) MessageEventSource;
-
 partial interface mixin WindowEventHandlers {
     attribute EventHandler onportalactivate;
 };