diff --git a/setup.py b/setup.py
index 59434e97e..18b9e08ba 100755
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
 from setuptools import setup, find_packages
 
 requires = ['itsdangerous', 'Jinja2', 'misaka>=2.0,<3.0', 'html5lib',
-            'werkzeug>=1.0', 'bleach', 'Flask-Caching>=1.9', 'Flask']
+            'werkzeug>=1.0,<2.1', 'bleach', 'Flask-Caching>=1.9', 'Flask']
 tests_require = ['pytest', 'pytest-cov']
 
 # https://packaging.python.org/en/latest/guides/making-a-pypi-friendly-readme/