diff --git a/types/chromecast-caf-sender/chromecast-caf-sender-tests.ts b/types/chromecast-caf-sender/chromecast-caf-sender-tests.ts
index b8e699ffd4..b4b0286636 100644
--- a/types/chromecast-caf-sender/chromecast-caf-sender-tests.ts
+++ b/types/chromecast-caf-sender/chromecast-caf-sender-tests.ts
@@ -1,6 +1,10 @@
+/// <reference lib="dom" />
+
 cast.framework.VERSION === "1.0.06";
 cast.framework.setLoggerLevel(cast.framework.LoggerLevel.DEBUG);
 
+window.__onGCastApiAvailable = (available: boolean) => {};
+
 const context = cast.framework.CastContext.getInstance();
 context.getCastState() === cast.framework.CastState.CONNECTED;
 context.getSessionState() === cast.framework.SessionState.NO_SESSION;
diff --git a/types/chromecast-caf-sender/index.d.ts b/types/chromecast-caf-sender/index.d.ts
index 10f2845316..5200d0fbc6 100644
--- a/types/chromecast-caf-sender/index.d.ts
+++ b/types/chromecast-caf-sender/index.d.ts
@@ -2,7 +2,7 @@
 // Project: https://developers.google.com/cast/docs/caf_receiver_overview
 // Definitions by: Samuel Maddock <https://github.com/samuelmaddock>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
-// TypeScript Version: 2.4
+// TypeScript Version: 3.0
 
 /// <reference types="chrome/chrome-cast" />
 
@@ -11,6 +11,7 @@
 ////////////////////
 interface Window {
   cast: typeof cast;
+  __onGCastApiAvailable(available: boolean): void;
 }
 
 ////////////////////