diff --git a/setup.py b/setup.py
index 322d58980bf4777644ea13c167e4df7690df31cc..9225bcb9bd7608d8300665bc9fe8a7559a55539a 100644
--- a/setup.py
+++ b/setup.py
@@ -41,6 +41,7 @@ requires = [
       "six",
       "sphinx",
       "sphinxcontrib-mscgen",
+      "sphinx-rtd-theme"
       "matplotlib>=1.4",
       "gevent",
       "pyzmq",