diff --git a/bukuserver/requirements.txt b/bukuserver/requirements.txt
index 69a6150..b13e5c8 100644
--- a/bukuserver/requirements.txt
+++ b/bukuserver/requirements.txt
@@ -10,7 +10,7 @@ Flask-Bootstrap>=3.3.7.1
 flask-paginate>=0.5.1
 flask-reverse-proxy-fix>=0.2.1
 Flask-WTF>=0.14.2
-Flask>=1.0.2
+Flask>=1.0.2,<2.0
 idna>=2.5
 itsdangerous>=0.24
 Jinja2>=2.10.1
diff --git a/setup.py b/setup.py
index d8f9882..4ddcd80 100644
--- a/setup.py
+++ b/setup.py
@@ -45,7 +45,7 @@ server_require = [
     'flask-paginate>=0.5.1',
     'flask-reverse-proxy-fix>=0.2.1',
     'Flask-WTF>=0.14.2',
-    'Flask>=1.0.2',
+    'Flask>=1.0.2,<2.0',
     'idna>=2.5',
     'itsdangerous>=0.24',
     'Jinja2>=2.10.1',