Fix and test for #645

Yuck, pickle is weird.  Closes #645.

1 files changed, 11 insertions, 8 deletions

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 764313f7..266a2402 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -28,20 +28,23 @@ class DictWithMetadata(dict):
     def __getstate__(self):
         """
         Used by pickle (e.g., caching).
-        Overriden to remove metadata from the dict, since it shouldn't be pickled
-        and may in some instances be unpickleable.
+        Overriden to remove the metadata from the dict, since it shouldn't be
+        pickled and may in some instances be unpickleable.
         """
-        # return an instance of the first dict in MRO that isn't a DictWithMetadata
-        for base in self.__class__.__mro__:
-            if not issubclass(base, DictWithMetadata) and issubclass(base, dict):
-                return base(self)
+        return dict(self)
 
 
-class SortedDictWithMetadata(SortedDict, DictWithMetadata):
+class SortedDictWithMetadata(SortedDict):
     """
     A sorted dict-like object, that can have additional properties attached.
     """
-    pass
+    def __getstate__(self):
+        """
+        Used by pickle (e.g., caching).
+        Overriden to remove the metadata from the dict, since it shouldn't be
+        pickle and may in some instances be unpickleable.
+        """
+        return SortedDict(self).__dict__
 
 
 def _is_protected_type(obj):