diff --git a/xep-0410.xml b/xep-0410.xml
index 3043712b..24f5c6d8 100644
--- a/xep-0410.xml
+++ b/xep-0410.xml
@@ -158,7 +158,11 @@
       <li><strong>Error (&lt;item-not-found&gt;)</strong>: the client is
 	joined, but the participant just changed their name (e.g. initiated by
 	a different client).</li>
-      <li><strong>Any other error</strong>: the client is probably not
+      <li><strong>Any other error</strong><note>Different service
+	  implementations will send different responses to a client that's not
+	  joined. The recommended error code is &lt;not-acceptable&gt;, however
+	  some servers will respond with &lt;not-allowed&gt; or
+	  &lt;bad-request&gt; as well.</note>: the client is probably not
 	joined any more. It should perform a re-join.</li>
       <li><strong>Timeout (no response)</strong>: the MUC service (or another
 	client) is unreachable. The client may indicate the status to the user