diff --git a/README.md b/README.md
index f0e275e..c5703bb 100644
--- a/README.md
+++ b/README.md
@@ -281,8 +281,13 @@ the platform, since it's an easy drop-in wherever you're handling events today.
 The proposed API shape is as follows:
 
 ```js
+dictionary ObservableEventListenerOptions {
+  boolean capture = false;
+  boolean passive;
+};
+
 partial interface EventTarget {
-  Observable on(DOMString type, optional AddEventListenerOptions options);
+  Observable on(DOMString type, optional ObservableEventListenerOptions options);
 };
 
 // `SubscribeCallback` is where the Observable "creator's" code lives. It's