diff --git a/requirements_dev.txt b/requirements_dev.txt
index 5c9dcb6..9beb6e2 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -1,11 +1,11 @@
-pip==8.1.2
+pip>=8.1.2
 bumpversion==0.5.3
 wheel==0.29.0
 watchdog==0.8.3
-flake8==2.6.0
-tox==2.3.1
-coverage==4.1
-Sphinx==1.4.8
-cryptography==1.7
-PyYAML==3.11
+flake8==3.3.0
+tox==2.7.0
+coverage==4.4.1
+Sphinx>=1.4.8
+cryptography==2.0
+PyYAML==3.12