diff --git a/docs/requirements.txt b/docs/requirements.txt
index 94ad4488..f3b5a044 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,3 @@
 sphinxcontrib-plantuml==0.18
 recommonmark==0.7.1
+sphinx_rtd_theme