diff --git a/requirements_dev.txt b/requirements_dev.txt
index 9d7da80..786fdc8 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -5,7 +5,7 @@ flake8==3.5.0
 tox==2.9.1
 coverage==4.4.2
 Sphinx==1.6.4
-cryptography==2.1.4
+cryptography==2.9.1
 PyYAML==3.12
 pytest==3.3.1
 pytest-runner==3.0