diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
index ed077ddb1e6..d6e1c4c92bf 100644
--- a/doc/src/sgml/client-auth.sgml
+++ b/doc/src/sgml/client-auth.sgml
@@ -381,7 +381,9 @@ hostnossl  <replaceable>database</replaceable>  <replaceable>user</replaceable>
       <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>