diff --git a/doc/requirements.txt b/doc/requirements.txt
index bd96d2483..815c6fe86 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -5,3 +5,4 @@ sphinx>=8
 ipython>=8
 pickleshare
 pygments>=2.7.4 # not directly required, pinned by Snyk to avoid a vulnerability
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability