diff --git a/requirements.txt b/requirements.txt
index 4b4f37d..c590e1f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-Flask>=0.12.2
+Flask>=0.12.2,<1.0
 Flask-SQLAlchemy>=2.3
 Flask-Login>=0.4.1
 Flask-User==0.6.19