diff --git a/appengine/flexible/pubsub/requirements.txt b/appengine/flexible/pubsub/requirements.txt
index 60f9fdda307..8c55c092198 100644
--- a/appengine/flexible/pubsub/requirements.txt
+++ b/appengine/flexible/pubsub/requirements.txt
@@ -1,3 +1,3 @@
 Flask==1.1.1
 google-cloud-pubsub==1.1.0
-gunicorn==20.0.4
+gunicorn==22.0.0