Index: django/core/cache/backends/locmem.py
===================================================================
--- django/core/cache/backends/locmem.py	(revision 16498)
+++ django/core/cache/backends/locmem.py	(working copy)
@@ -31,7 +31,8 @@
             exp = self._expire_info.get(key)
             if exp is None or exp <= time.time():
                 try:
-                    self._set(key, pickle.dumps(value), timeout)
+                    pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+                    self._set(key, pickled, timeout)
                     return True
                 except pickle.PickleError:
                     pass
@@ -49,7 +50,8 @@
                 return default
             elif exp > time.time():
                 try:
-                    return pickle.loads(self._cache[key])
+                    pickled = self._cache[key]
+                    return pickle.loads(pickled)
                 except pickle.PickleError:
                     return default
         finally:
@@ -78,7 +80,8 @@
         self.validate_key(key)
         self._lock.writer_enters()
         try:
-            self._set(key, pickle.dumps(value), timeout)
+            pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+            self._set(key, pickled, timeout)
         except pickle.PickleError:
             pass
         finally:
Index: django/core/cache/backends/db.py
===================================================================
--- django/core/cache/backends/db.py	(revision 16498)
+++ django/core/cache/backends/db.py	(working copy)
@@ -79,7 +79,8 @@
         exp = datetime.fromtimestamp(time.time() + timeout).replace(microsecond=0)
         if num > self._max_entries:
             self._cull(db, cursor, now)
-        encoded = base64.encodestring(pickle.dumps(value, 2)).strip()
+        pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+        encoded = base64.encodestring(pickled).strip()
         cursor.execute("SELECT cache_key, expires FROM %s WHERE cache_key = %%s" % table, [key])
         try:
             result = cursor.fetchone()