diff --git a/tiramisu/option/option.py b/tiramisu/option/option.py
index 600cf2a..619b2c0 100644
--- a/tiramisu/option/option.py
+++ b/tiramisu/option/option.py
@@ -465,7 +465,21 @@ class DomainnameOption(Option):
             raise ValueError(_('allow_without_dot must be a boolean'))
         extra['_allow_ip'] = allow_ip
         extra['_allow_without_dot'] = allow_without_dot
-        extra['_domain_re'] = re.compile(r'^[a-z\d][a-z\d\-]*$')
+        # FIXME should be
+        # regexp = r'^((?!-)[a-z0-9-]{1,63}(?<!-)\.{0,1})$'
+        if type_ == 'domainname':
+            if allow_without_dot:
+                min_time = 0
+            else:
+                min_time = 1
+            regexp = r'((?!-)[a-z0-9-]{{{1},{0}}}\.){{{1},}}[a-z0-9-]{{1,{0}}}'.format(self._get_len(type_), min_time)
+        else:
+            regexp = r'((?!-)[a-z0-9-]{{1,{0}}})'.format(self._get_len(type_))
+        if allow_ip:
+            regexp = r'^(?:{0}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){{3}}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))$'.format(regexp)
+        else:
+            regexp = r'^{0}$'.format(regexp)
+        extra['_domain_re'] = re.compile(regexp)
         extra['_has_upper'] = re.compile('[A-Z]')
 
         super(DomainnameOption, self).__init__(name, doc, default=default,
@@ -480,6 +494,12 @@ class DomainnameOption(Option):
                                                warnings_only=warnings_only,
                                                extra=extra)
 
+    def _get_len(self, type_):
+        if type_ == 'netbios':
+            return 15
+        else:
+            return 63
+
     def _validate(self, value, context=undefined, current_opt=undefined):
         err = self._impl_valid_unicode(value)
         if err:
@@ -505,10 +525,7 @@ class DomainnameOption(Option):
                 pass
             else:
                 raise ValueError(_('must not be an IP'))
-        if self._get_extra('_dom_type') == 'netbios':
-            part_name_length = 15
-        else:
-            part_name_length = 63
+        part_name_length = self._get_len(self._get_extra('_dom_type'))
         if self._get_extra('_dom_type') == 'domainname':
             if not self._get_extra('_allow_without_dot') and not "." in value:
                 return ValueError(_("must have dot"))
@@ -522,26 +539,13 @@ class DomainnameOption(Option):
             return _valid_length(value)
 
     def _second_level_validation(self, value, warnings_only):
-        def _valid_char(val):
-            if self._get_extra('_has_upper').search(val):
-                return ValueError(_('some characters are uppercase'))
-            if not self._get_extra('_domain_re').search(val):
-                if warnings_only:
-                    return ValueError(_('some characters may cause problems'))
-                else:
-                    return ValueError()
-        #not for IP
-        if self._get_extra('_allow_ip') is True:
-            try:
-                IP('{0}/32'.format(value))
-                return
-            except ValueError:
-                pass
-        if self._get_extra('_dom_type') == 'domainname':
-            for dom in value.split('.'):
-                return _valid_char(dom)
-        else:
-            return _valid_char(value)
+        if self._get_extra('_has_upper').search(value):
+            return ValueError(_('some characters are uppercase'))
+        if not self._get_extra('_domain_re').search(value):
+            if warnings_only:
+                return ValueError(_('some characters may cause problems'))
+            else:
+                return ValueError()
 
 
 class URLOption(DomainnameOption):