Index: django/newforms/fields.py
===================================================================
--- django/newforms/fields.py	(Revision 6903)
+++ django/newforms/fields.py	(Arbeitskopie)
@@ -750,3 +750,6 @@
 
     def __init__(self, *args, **kwargs):
         super(IPAddressField, self).__init__(ipv4_re, *args, **kwargs)
+
+    def clean(self, value):
+        return super(RegexField, self).clean(value) or None