diff --git a/tox.ini b/tox.ini
index 560033d0..615850c0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,7 +19,7 @@ commands =
 
 [testenv:docs]
 basepython = python
-deps = Sphinx
+deps = Sphinx sphinx-rtd-theme
 changedir = docs
 commands =
         pip install --upgrade Tailbone rattail[auth,bouncer] rattail-tempmon