diff --git a/requirements.txt b/requirements.txt
index d294d4fd73..55351c1052 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 Babel!=2.4.0,>=2.3.4 # BSD
 croniter>=0.3.4 # MIT License
-cryptography>=1.6 # BSD/Apache-2.0
+cryptography!=2.0,>=1.6 # BSD/Apache-2.0
 debtcollector>=1.2.0 # Apache-2.0
 eventlet!=0.18.3,!=0.20.1,<0.21.0,>=0.18.2 # MIT
 keystoneauth1>=3.0.1 # Apache-2.0