diff --git a/ddclient.in b/ddclient.in
index c6d22d0..0a86822 100755
--- a/ddclient.in
+++ b/ddclient.in
@@ -587,8 +587,8 @@ my %variables = (
         'fwv4-skip'           => setv(T_STRING,0, 0, undef,                undef),
         'fwv6'                => setv(T_ANY,   0, 0, '',                   undef),
         'fwv6-skip'           => setv(T_STRING,0, 0, undef,                undef),
-        'fw-login'            => setv(T_LOGIN, 1, 0, '',                   undef),
-        'fw-password'         => setv(T_PASSWD,1, 0, '',                   undef),
+        'fw-login'            => setv(T_LOGIN, 1, 0, undef,                undef),
+        'fw-password'         => setv(T_PASSWD,1, 0, undef,                undef),
         'cmd'                 => setv(T_PROG,  0, 0, '',                   undef),
         'cmd-skip'            => setv(T_STRING,0, 0, undef,                undef),
         'cmdv4'               => setv(T_PROG,  0, 0, '',                   undef),
@@ -620,9 +620,9 @@ my %variables = (
     },
     'protocol-common-defaults' => {
         'server'              => setv(T_FQDNP, 1, 0, 'members.dyndns.org', undef),
-        'login'               => setv(T_LOGIN, 1, 0, '',                   undef),
-        'password'            => setv(T_PASSWD,1, 0, '',                   undef),
-        'host'                => setv(T_STRING,1, 1, '',                   undef),
+        'login'               => setv(T_LOGIN, 1, 0, undef,                undef),
+        'password'            => setv(T_PASSWD,1, 0, undef,                undef),
+        'host'                => setv(T_STRING,1, 1, undef,                undef),
 
         'use'                 => setv(T_USE,   0, 0, 'ip',                 undef),
         'usev4'               => setv(T_USEV4, 0, 0, 'disabled',           undef),
@@ -741,7 +741,7 @@ my %protocols = (
             'static'       => setv(T_BOOL,   0, 1, 0,                              undef),
             'ttl'          => setv(T_NUMBER, 1, 0, 1,                              undef),
             'wildcard'     => setv(T_BOOL,   0, 1, 0,                              undef),
-            'zone'         => setv(T_FQDN,   1, 0, '',                             undef),
+            'zone'         => setv(T_FQDN,   1, 0, undef,                          undef),
         },
     },
     'cloudns' => {
@@ -763,7 +763,7 @@ my %protocols = (
             %{$variables{'protocol-common-defaults'}},
             'login' => undef,
             'server' => setv(T_FQDNP, 1, 0, 'api.digitalocean.com', undef),
-            'zone'   => setv(T_FQDN,  1, 0, '',                     undef),
+            'zone'   => setv(T_FQDN,  1, 0, undef,                  undef),
         },
     },
     'dinahosting' => {
@@ -902,7 +902,7 @@ my %protocols = (
             'min-interval' => setv(T_DELAY,  0, 0, interval('5m'),                 0),
             'server'       => setv(T_FQDNP,  1, 0, 'api.godaddy.com/v1/domains',   undef),
             'ttl'          => setv(T_NUMBER, 1, 0, 600,                            undef),
-            'zone'         => setv(T_FQDN,   1, 0, '',                             undef),
+            'zone'         => setv(T_FQDN,   1, 0, undef,                          undef),
         },
     },
     'googledomains' => {
@@ -925,7 +925,7 @@ my %protocols = (
             'min-interval' => setv(T_DELAY,  0, 0, interval('1m'),                 0),
             'server'       => setv(T_FQDNP,  1, 0, 'dns.hetzner.com/api/v1',       undef),
             'ttl'          => setv(T_NUMBER, 0, 0, 60,                             60),
-            'zone'         => setv(T_FQDN,   1, 0, '',                             undef),
+            'zone'         => setv(T_FQDN,   1, 0, undef,                          undef),
         },
     },
     'mythicdyn' => {
@@ -991,7 +991,7 @@ my %protocols = (
             'login' => setv(T_LOGIN,  1, 0, '/usr/bin/nsupdate', undef),
             'tcp'   => setv(T_BOOL,   0, 1, 0,                   undef),
             'ttl'   => setv(T_NUMBER, 0, 1, 600,                 undef),
-            'zone'  => setv(T_STRING, 1, 1, '',                  undef),
+            'zone'  => setv(T_STRING, 1, 1, undef,               undef),
         },
     },
     'ovh' => {
@@ -1012,8 +1012,8 @@ my %protocols = (
             %{$variables{'protocol-common-defaults'}},
             'login' => undef,
             'password' => undef,
-            'apikey'         => setv(T_PASSWD, 1, 0, '',         undef),
-            'secretapikey'   => setv(T_PASSWD, 1, 0, '',         undef),
+            'apikey'         => setv(T_PASSWD, 1, 0, undef,      undef),
+            'secretapikey'   => setv(T_PASSWD, 1, 0, undef,      undef),
             'root-domain'    => setv(T_OFQDN,  0, 0, '',         undef),
             'on-root-domain' => setv(T_BOOL,   0, 0, 0,          undef),
         },