diff --git a/setup.py b/setup.py
index a78d2afa..3c101d53 100644
--- a/setup.py
+++ b/setup.py
@@ -19,7 +19,7 @@
     ],
     'doc': [
         "Sphinx>=1.6.5,<2",
-        "sphinx_rtd_theme>=0.1.9",
+        "sphinx_rtd_theme>=0.1.9,<1",
         "towncrier>=19.2.0, <20",
     ],
     'dev': [