diff --git a/docs/requirements.txt b/docs/requirements.txt
index 37806c99d54b087431cfdac5174c3f4901852823..fa68258b1d84063d6ca0fb46f55e80e414eb9bdd 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,3 @@
 sphinx==2.1.0
+mistune
 sphinx_rtd_theme