diff --git a/requirements.txt b/requirements.txt
index 6388a68b..dfddd63a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,3 +10,4 @@ pathlib2
 PyPDF2>=2.0.0
 reportlab>=3.5.0
 streamlit
+tornado>=6.5.3 # not directly required, pinned by Snyk to avoid a vulnerability