diff --git a/requirements.txt b/requirements.txt
index b979a07..531d481 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-tornado==6.4
+tornado==6.3.3
 isodate==0.6.1
 pytest==8.0.1
 schwifty==2023.06.0