diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
index ccd748d264a..1ff7852ab55 100644
--- a/doc/src/sgml/client-auth.sgml
+++ b/doc/src/sgml/client-auth.sgml
@@ -413,7 +413,9 @@ hostnogssenc  <replaceable>database</replaceable>  <replaceable>user</replaceabl
       <para>
        Specifies the authentication method to use when a connection matches
        this record. The possible choices are summarized here; details
-       are in <xref linkend="auth-methods"/>.
+       are in <xref linkend="auth-methods"/>.  All the options
+       are lower case and treated case sensitively, so even acronyms like
+       <literal>ldap</literal> must be specified as lower case.
 
        <variablelist>
         <varlistentry>