diff --git a/getusermedia.html b/getusermedia.html
index 2a02151e..c7c81653 100644
--- a/getusermedia.html
+++ b/getusermedia.html
@@ -3436,7 +3436,7 @@ <h3>{{DeviceChangeEvent}}</h3>
         <pre class="idl"
 >[Exposed=Window]
 interface DeviceChangeEvent : Event {
-  constructor(DOMString type, DeviceChangeEventInit eventInitDict);
+  constructor(DOMString type, optional DeviceChangeEventInit eventInitDict = {});
   [SameObject] readonly attribute FrozenArray&lt;MediaDeviceInfo&gt; devices;
 };</pre>
         <section>