Index: django/db/models/manipulators.py
===================================================================
--- django/db/models/manipulators.py	(revision 6778)
+++ django/db/models/manipulators.py	(working copy)
@@ -189,7 +189,16 @@
                             else:
                                 param = f.get_default()
                         else:
-                            param = f.get_manipulator_new_data(rel_new_data, rel=True)
+                            if getattr(f, 'auto_now', False):
+                                param = 'NOW()'
+                            elif getattr(f, 'auto_now_add', False):
+                                if old_rel_obj:
+                                    param = getattr(old_rel_obj, f.column)
+                                else:
+                                    param = 'NOW()'
+                            else:
+                                param = f.get_manipulator_new_data(rel_new_data, rel=True)
+                            
                         if param != None:
                             params[f.attname] = param