diff --git a/reference/soap/soapclient/soapclient.xml b/reference/soap/soapclient/soapclient.xml
index fb05cec5a9..6d25d03d0f 100644
--- a/reference/soap/soapclient/soapclient.xml
+++ b/reference/soap/soapclient/soapclient.xml
@@ -67,7 +67,11 @@
        <literal>proxy_port</literal>, <literal>proxy_login</literal>
        and <literal>proxy_password</literal> are also available.
        For HTTPS client certificate authentication use
-       <literal>local_cert</literal> and <literal>passphrase</literal> options.
+       <literal>local_cert</literal> and <literal>passphrase</literal> options. An 
+       authentication may be supplied in the <literal>authentication</literal> 
+       option. The authentication method may be either 
+       <constant>SOAP_AUTHENTICATION_BASIC</constant> (default) or 
+       <constant>SOAP_AUTHENTICATION_DIGEST</constant>.
       </para>
       <para>
        The <literal>compression</literal> option allows to use compression