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):