diff --git a/docs/requirements.txt b/docs/requirements.txt
index 802f83249..de0db78bb 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -8,3 +8,4 @@ pyusb
 -e git://github.com/greatscottgadgets/luna.git#egg=luna
 pyvcd
 pyserial~=3.4
+sphinx_rtd_theme==1.3.0
\ No newline at end of file