diff --git a/requirements_dev.txt b/requirements_dev.txt
index c3985d2..7df6215 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -2,9 +2,9 @@ bumpversion==0.5.3
 wheel==0.31.1
 watchdog==0.8.3
 flake8==3.5.0
-tox==3.0.0
+tox==3.1.2
 coverage==4.5.1
 Sphinx==1.7.5
-sphinx-rtd-theme==0.3.1
+sphinx-rtd-theme==0.4.0
 cryptography==2.2.2
-PyYAML==3.12
+PyYAML==3.13