diff --git a/doc/config.html b/doc/config.html
index 44172867..ed145621 100755
--- a/doc/config.html
+++ b/doc/config.html
@@ -1374,6 +1374,10 @@ Subst Author = $author from $remote_host
         <pre>
 Subst on reply subject = Re: $subject
 </pre>
+        Note that this option works only for the first reply. So a 
+        reply-to-a-reply would still have <b>Re: &lt;old subject&gt;</b>
+        and not <b>Re: Re: &lt;old subject&gt;</b>. If you want the substitution
+        for all replies, please use <code><b>Preset on reply</b></code> instead.
       </li>
       <li>
         <b><code>Subst on edit &lt;attribute &gt; =