diff --git a/docs/requirements.txt b/docs/requirements.txt
index a62bf415..57064f48 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,3 +1,4 @@
+mistune<=0.8.4
 m2r
 sphinxcontrib-apidoc
 docutils<=0.17.1