diff --git a/requirements.txt b/requirements.txt
index 7f3e6c5..12e0759 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 Flask == 0.10.1
 Pygments == 2.1
-tornado == 4.3
+tornado==6.5.3
 WTForms == 2.1
 werkzeug>=3.0.6 # not directly required, pinned by Snyk to avoid a vulnerability