diff --git a/docs/requirements.txt b/docs/requirements.txt
index 5de8cc6b..31a23482 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,4 @@
+# Required library
+Sphinx==1.5.3
 # Docs template
 https://github.com/graphql-python/graphene-python.org/archive/docs.zip