diff --git a/requirements.txt b/requirements.txt
index 92e35d3..56ecf62 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,4 +7,5 @@ matplotlib
 mpl-finance
 scikit-learn
 seaborn
-v20
\ No newline at end of file
+v20
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability
\ No newline at end of file