Ticket #1207: dont-clobber-new_data.patch

django/forms/__init__.py

@@ -99 +99 @@
         expected to deal with invalid input.
         """
         for field in self.fields:
-            field.convert_post_data(new_data)
+            if field.field_name in new_data:
+                field.convert_post_data(new_data)
 
 class FormWrapper:
     """