diff --git a/requirements.txt b/requirements.txt
index 8895a2a..ba61677 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,3 +2,4 @@ sphinx==1.6.7
 sphinx_rtd_theme==0.2.4
 git+https://github.com/sphinx-contrib/redirects@c25afdc3d812c983560750916c9616f4cb6f98eb
 m2r==0.2.1
+docutils<0.18