diff --git a/docs/requirements.txt b/docs/requirements.txt
index 702066a..c45a509 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -2,3 +2,4 @@ sphinx==5.0.2
 sphinx_rtd_theme==1.0.0
 readthedocs-sphinx-search==0.1.2
 jinja2<3.1.0
+markdown<3.4.0