diff --git a/tox.ini b/tox.ini
index f298f79e7..830235dfc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,6 +16,7 @@ deps =
     django110: Django>=1.10, <1.11
     django111: Django>=1.11, <2.0
     py27: mock
+    py33: cryptography==1.9
     boto3>=1.2.3
     boto>=2.32.0
     dropbox>=8.0.0