Index: django/db/models/fields/__init__.py

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--- django/db/models/fields/__init__.py	(revision 6918)

+++ django/db/models/fields/__init__.py	(working copy)

@@ -906,6 +906,11 @@

     def get_manipulator_field_objs(self):
         return [oldforms.NullBooleanField]
 
+    def formfield(self, **kwargs):
+        defaults = {'required': not self.blank, 'label': capfirst(self.verbose_name), 'help_text': self.help_text}
+        defaults.update(kwargs)
+        return forms.NullBooleanField(**defaults)
+
 class PhoneNumberField(IntegerField):
     def get_manipulator_field_objs(self):
         return [oldforms.PhoneNumberField]