diff --git a/requirements.txt b/requirements.txt
index 5438905..df11c79 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,3 +19,4 @@ simplejson==3.17.0
 yfinance==0.1.54
 pandas-datareader==0.8.1
 vaderSentiment==3.3.1
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability