diff --git a/requirements.txt b/requirements.txt
index bed1e03..0ab9c45 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -18,7 +18,7 @@ Flask-Migrate==3.0.1
 Flask-Moment==1.0.1
 Flask-SQLAlchemy==2.5.1
 Flask-WTF==0.15.1
-greenlet==2.0.1
+#greenlet==2.0.1 (trial update from 1.1.0 -> 2.0.1, failed)
 httpie==2.4.0
 idna==2.10
 itsdangerous==2.0.1