diff --git a/docs/requirements.txt b/docs/requirements.txt
index a89dfbf8..400b4741 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -3,3 +3,4 @@ sphinx-rtd-theme==0.5.0
 m2r==0.2.1
 docutils==0.16
 peleffy
+mistune==0.8.4