From 5df8f749e6338c85a091f41803e6ecb280fc9f70 Mon Sep 17 00:00:00 2001
From: Loic Bistuer <loic.bistuer@sixmedia.com>
Date: Mon, 2 Sep 2013 01:21:08 +0700
Subject: [PATCH] Fixed #20978 -- Made deletion.SET_NULL more friendly for
 MigrationWriter.serialize.

---
 django/db/models/deletion.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/django/db/models/deletion.py b/django/db/models/deletion.py
index 769e5b9bb6..6f89da7417 100644
--- a/django/db/models/deletion.py
+++ b/django/db/models/deletion.py
@@ -38,7 +38,8 @@ def SET(value):
     return set_on_delete
 
 
-SET_NULL = SET(None)
+def SET_NULL(collector, field, sub_objs, using):
+    collector.add_field_update(field, None, sub_objs)
 
 
 def SET_DEFAULT(collector, field, sub_objs, using):