diff --git a/requirements.txt b/requirements.txt
index dcdb035c..10ebb3eb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -22,3 +22,4 @@ logzero>=1.5.0
 xmltodict>=0.11.0
 plotly>=3.10.0
 pyyaml>=3.12
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability