diff --git a/requirements.txt b/requirements.txt
index f93ae9e9f..4b919895e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,7 +10,7 @@ Jinja2!=2.9.0,!=2.9.1,!=2.9.2,!=2.9.3,!=2.9.4,>=2.8 # BSD License (3 clause)
 keystonemiddleware>=4.12.0 # Apache-2.0
 lxml!=3.7.0,>=2.3 # BSD
 Routes>=2.3.1 # MIT
-cryptography>=1.6 # BSD/Apache-2.0
+cryptography!=2.0,>=1.6 # BSD/Apache-2.0
 WebOb>=1.7.1 # MIT
 greenlet>=0.3.2 # MIT
 PasteDeploy>=1.5.0 # MIT