diff --git a/en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml b/en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml
index 76fd35393e..e007df6db7 100644
--- a/en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml
+++ b/en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml
@@ -778,7 +778,8 @@ mountd_flags="-r"</programlisting>
 	following <filename>/etc/exports</filename> would be
 	invalid:</para>
 
-      <programlisting>/usr/src   client
+      <programlisting># Invalid when /usr is one file system
+/usr/src   client
 /usr/ports client</programlisting>
 
       <para>One filesystem, <filename>/usr</filename>, has two lines