diff --git a/lib/hk-util.js b/lib/hk-util.js
index bc2c39f35..4dab6cafc 100644
--- a/lib/hk-util.js
+++ b/lib/hk-util.js
@@ -1028,6 +1028,17 @@ HK.onChannelMessage = function (Env, Server, channel, msgStruct, cb) {
             if (!_metadata) { return; }
             metadata = _metadata;
 
+            if (metadata?.restricted) {
+                const userId = msgStruct[1];
+                // If userId is defined (not a private message) and the user
+                // is not a member of this restricted channel, prevent them
+                // from broadcasting to the pad until they have joined it
+                if (userId && !Server.channelContainsUser(channel.id, userId)) {
+                    cb('EFORBIDDEN');
+                    return void w.abort();
+                }
+            }
+
             // don't write messages to expired channels
             if (checkExpired(Env, Server, channel)) {
                 cb('EEXPIRED');