diff --git a/dropbox/session.py b/dropbox/session.py
index bf54f842..cd47292c 100644
--- a/dropbox/session.py
+++ b/dropbox/session.py
@@ -41,6 +41,7 @@
 # TODO(kelkabany): We probably only want to instantiate this once so that even
 # if multiple Dropbox objects are instantiated, they all share the same pool.
 class _SSLAdapter(HTTPAdapter):
+    _ca_certs = None
 
     def __init__(self, *args, **kwargs):
         self._ca_certs = kwargs.pop("ca_certs", None) or _TRUSTED_CERT_FILE
diff --git a/test/unit/test_dropbox_unit.py b/test/unit/test_dropbox_unit.py
index 259d43de..c1fd6058 100644
--- a/test/unit/test_dropbox_unit.py
+++ b/test/unit/test_dropbox_unit.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 
 import mock
+import pickle
 
 import pytest
 
@@ -404,3 +405,10 @@ def test_team_client_as_user(self, session_instance):
                       app_secret=APP_SECRET,
                       session=session_instance)
         dbx.as_user(TEAM_MEMBER_ID)
+
+
+class TestSession:
+    def test_pickle_session(self):
+        session_obj = create_session()
+        pickled_session = pickle.dumps(session_obj)
+        pickle.loads(pickled_session)