diff --git a/page-to-extension-messaging/content-script.js b/page-to-extension-messaging/content-script.js
index 50cb715..01646c9 100644
--- a/page-to-extension-messaging/content-script.js
+++ b/page-to-extension-messaging/content-script.js
@@ -4,7 +4,7 @@ If the message was from the page script, show an alert.
 */
 window.addEventListener("message", function(event) {
   if (event.source == window &&
-      event.data.direction &&
+      event.data &&
       event.data.direction == "from-page-script") {
     alert("Content script received message: \"" + event.data.message + "\"");
   }