diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91709175..be45c61f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # CHANGELOG
 
+
+## X.X.X (comming soon)
+
+- Improve error message when calling `postMessage` to a closed channel.
+
 ## 4.9.0 (23 December 2021)
 
 Bugfixes:
diff --git a/src/broadcast-channel.js b/src/broadcast-channel.js
index 4c8ecb19..d9114829 100644
--- a/src/broadcast-channel.js
+++ b/src/broadcast-channel.js
@@ -112,7 +112,13 @@ BroadcastChannel.prototype = {
         if (this.closed) {
             throw new Error(
                 'BroadcastChannel.postMessage(): ' +
-                'Cannot post message after channel has closed'
+                'Cannot post message after channel has closed ' +
+                /**
+                 * In the past when this error appeared, it was realy hard to debug.
+                 * So now we log the msg together with the error so it at least
+                 * gives some clue about where in your application this happens.
+                 */
+                JSON.stringify(msg)
             );
         }
         return _post(this, 'message', msg);