diff --git a/README b/README
index c7ecc75..7461f64 100644
--- a/README
+++ b/README
@@ -188,6 +188,12 @@ specify the path where X509 certificates are stored. This is
 required if 'https' or 'ldaps' are used in 'url' and 'ldap_uri'
 respectively.
 
+proxy::
+specify a proxy to connect to the validation server. Valid schemes are
+socks4://, socks4a://, socks5:// or socks5h://. Socks5h asks the proxy
+to do the dns resolving. If no scheme or port is specified HTTP proxy
+port 1080 will be used.
+
 verbose_otp::
    This argument is used to show the OTP (One-Time Password) when it
    is entered, i.e. to enable terminal echo of entered characters.