diff --git a/docs/requirements.txt b/docs/requirements.txt
index abfe53042..54a940c71 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -6,3 +6,4 @@ readthedocs-sphinx-ext
 recommonmark>=0.4.0
 sphinx>=1.3.6,<1.6
 sphinx_rtd_theme
+mistune>=2.0.1 # not directly required, pinned by Snyk to avoid a vulnerability