diff --git a/requirements.docs.txt b/requirements.docs.txt
index 76ac2e5..5eff65c 100644
--- a/requirements.docs.txt
+++ b/requirements.docs.txt
@@ -17,4 +17,5 @@ sphinx==1.7.5 # pyup: ignore
 pooch
 dynetx
 matplotlib
-mock
\ No newline at end of file
+mock
+sphinx_rtd_theme
\ No newline at end of file