diff --git a/docs-requirements.txt b/docs-requirements.txt
index 8a7c900..143634f 100644
--- a/docs-requirements.txt
+++ b/docs-requirements.txt
@@ -1,7 +1,7 @@
 recommonmark
 # sphinxcontrib-httpexample
 sphinx==1.8.2
-sphinx-rtd-theme
+sphinx-rtd-theme==1.2.1
 sphinxcontrib-apidoc
 sphinxcontrib.httpdomain==1.7.0
 sphinxcontrib-httpexample==0.9.0