diff --git a/source b/source index bfa2b6782ef..6f449133287 100644 --- a/source +++ b/source @@ -66310,12 +66310,14 @@ console.log(plasticButton.outerHTML); // will output '<button is="plastic-but 
[Exposed=Window]
 interface CustomElementRegistry {
-  [CEReactions] void define(DOMString name, Function constructor, optional ElementDefinitionOptions options);
+  [CEReactions] void define(DOMString name, CustomElementConstructor constructor, optional ElementDefinitionOptions options);
   any get(DOMString name);
   Promise<void> whenDefined(DOMString name);
   [CEReactions] void upgrade(Node root);
 };
 
+callback CustomElementConstructor = any ();
+
 dictionary ElementDefinitionOptions {
   DOMString extends;
 };