diff --git a/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py b/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
index 8ab776f53d..01ac12d58e 100644
--- a/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
+++ b/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
@@ -256,7 +256,7 @@ class CourseStructureCache(object):
             return None
 
         with TIMER.timer("CourseStructureCache.set", course_context) as tagger:
-            pickled_data = pickle.dumps(structure, 2)  # Protocol can't be incremented until cache is cleared
+            pickled_data = pickle.dumps(structure, 4)  # Protocol can't be incremented until cache is cleared
             tagger.measure('uncompressed_size', len(pickled_data))
 
             # 1 = Fastest (slightly larger results)
diff --git a/openedx/core/lib/cache_utils.py b/openedx/core/lib/cache_utils.py
index b7d016fee7..10029cfc1a 100644
--- a/openedx/core/lib/cache_utils.py
+++ b/openedx/core/lib/cache_utils.py
@@ -153,7 +153,7 @@ class process_cached(object):  # pylint: disable=invalid-name
 
 def zpickle(data):
     """Given any data structure, returns a zlib compressed pickled serialization."""
-    return zlib.compress(pickle.dumps(data, 2))  # Keep this constant as we upgrade from python 2 to 3.
+    return zlib.compress(pickle.dumps(data, 4))  # Keep this constant as we upgrade from python 2 to 3.
 
 
 def zunpickle(zdata):
diff --git a/openedx/core/lib/session_serializers.py b/openedx/core/lib/session_serializers.py
index c1ff9ae51d..9a401c6152 100644
--- a/openedx/core/lib/session_serializers.py
+++ b/openedx/core/lib/session_serializers.py
@@ -7,16 +7,15 @@ import six
 
 class PickleV2Serializer(object):
     """
-    Lock the pickle serializer to version 2 of the protocol
-    because we don't want python 2 to be able to read session
-    data written by python3 while both are running at the same
-    time in production.
+    Set the pickle protocol version explicitly because we don't want
+    to have session thrashing when we upgrade to newer versions of
+    python.
 
     Based on the PickleSerializer built into django:
     https://github.com/django/django/blob/master/django/contrib/sessions/serializers.py
     """
 
-    protocol = 2
+    protocol = 4
 
     def dumps(self, obj):
         """
@@ -28,10 +27,4 @@ class PickleV2Serializer(object):
         """
         Return a python object from pickled data.
         """
-        if six.PY2:
-            # Params used below don't exist in python 2
-            return pickle.loads(data)
-        else:
-            # See notes here about pickling python2 objects in python3
-            # https://docs.python.org/3/library/pickle.html#pickle.Unpickler
-            return pickle.loads(data, encoding='latin1')  # pylint: disable=unexpected-keyword-arg
+        return pickle.loads(data)