diff --git a/requirements.txt b/requirements.txt
index a66a45d40..a17edf469 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -27,6 +27,7 @@ Flask-SQLAlchemy==2.3.2
 Flask-WTF==1.0.0
 gunicorn==20.1.0
 gevent==1.4.0
+greenlet==0.4.17
 htmlmin==0.1.12
 idna==2.10
 itsdangerous==2.0.1