diff --git a/requirements.txt b/requirements.txt
index ecbbfaa..d9a2c8c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,3 +11,4 @@ scikit-image >= 0.15
 scikit-learn >= 0.20
 snakeviz >= 2.1
 watermark >= 2.2
+tornado>=6.3.2 # not directly required, pinned by Snyk to avoid a vulnerability