diff --git a/requirements.txt b/requirements.txt
index 0d78461..83a1b00 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -20,3 +20,4 @@ pytest-xdist
 pytest-rerunfailures
 pytest-mpl
 pillow>=6.2.3 # not directly required, pinned by Snyk to avoid a vulnerability
+tornado>=6.3.3 # not directly required, pinned by Snyk to avoid a vulnerability