--- doc/src/sgml/config.sgml.orig	2008-10-18 00:08:50.000000000 -0500
+++ doc/src/sgml/config.sgml	2008-10-18 00:10:58.000000000 -0500
@@ -337,6 +337,12 @@
         same port number is used for all IP addresses the server listens on.
         This parameter can only be set at server start.
        </para>
+       <para>
+        This setting also determines the key used for the shared memory
+        segment.  Because of that, two servers can not be started on the
+        same port, even if they have different listen_addresses, unless
+        they are also running under two different userids.
+       </para>
       </listitem>
      </varlistentry>