diff --git a/django/contrib/formtools/preview.py b/django/contrib/formtools/preview.py
index 2e4fb92cda..bd0ce5cbb7 100644
--- a/django/contrib/formtools/preview.py
+++ b/django/contrib/formtools/preview.py
@@ -109,7 +109,7 @@ class FormPreview(object):
         data = [(bf.name, bf.data) for bf in form] + [settings.SECRET_KEY]
         # Use HIGHEST_PROTOCOL because it's the most efficient. It requires
         # Python 2.3, but Django requires 2.3 anyway, so that's OK.
-        pickled = pickle.dumps(data, protocol=pickle.HIGHEST_PROTOCOL)
+        pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
         return md5.new(pickled).hexdigest()
 
     def failed_hash(self, request):
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 624a7d6803..0107e7f916 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -173,11 +173,12 @@ class Options(object):
         Initialises the field name -> field object mapping.
         """
         cache = dict([(f.name, (f, True, False)) for f in self.fields])
-        cache.update([(f.name, (f, True, True)) for f in self.many_to_many])
-        cache.update([(f.field.related_query_name(), (f, False, True))
-                for f in self.get_all_related_many_to_many_objects()])
-        cache.update([(f.field.related_query_name(), (f, False, False))
-                for f in self.get_all_related_objects()])
+        for f in self.many_to_many:
+            cache[f.name] = (f, True, True)
+        for f in self.get_all_related_many_to_many_objects():
+            cache[f.field.related_query_name()] = (f, False, True)
+        for f in self.get_all_related_objects():
+            cache[f.field.related_query_name()] = (f, False, False)
         if app_cache_ready():
             self._name_map = cache
         return cache
diff --git a/django/db/models/query.py b/django/db/models/query.py
index 880562960c..5fae43841c 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -395,7 +395,8 @@ class ValuesQuerySet(QuerySet):
         if self._fields:
             opts = self.model._meta
             all = dict([(field.column, field) for field in opts.fields])
-            all.update([(field.name, field) for field in opts.fields])
+            for field in opts.fields:
+                all[field.name] = field
             if not self.query.extra_select:
                 try:
                     fields = [all[f] for f in self._fields]