diff --git a/setup.py b/setup.py
index 0830e60ebb8ea66492c994d859b98db72865abe8..20b37a85a5e108787b0549186893c88c7ce1519e 100644
--- a/setup.py
+++ b/setup.py
@@ -40,6 +40,7 @@ tests_require = [
 
 docs_require = [
     'Sphinx',
+    'sphinx_rtd_theme',
     ]
 
 setup(