Don't bork if request attribute is not set.

1 files changed, 1 insertions, 1 deletions

diff --git a/djangorestframework/serializer.py b/djangorestframework/serializer.py
index ffe9d8cb..027c9daf 100644
--- a/djangorestframework/serializer.py
+++ b/djangorestframework/serializer.py
@@ -180,7 +180,7 @@ class Serializer(object):
             stack.append(obj)
 
         return related_serializer(depth=depth, stack=stack).serialize(
-            obj, request=self.request)
+            obj, request=getattr(self, 'request', None))
 
     def serialize_max_depth(self, obj):
         """