diff --git a/python-package/setup.cfg b/python-package/setup.cfg
index 4bc1a94b..1071ddc4 100644
--- a/python-package/setup.cfg
+++ b/python-package/setup.cfg
@@ -48,7 +48,7 @@ install_requires =
     ruamel.yaml >= 0.16
     yamale >= 3.0
     # for WebServer:
-    werkzeug >= 1.0
+    werkzeug >= 1.0 , < 2.0
     mako >= 1.1
     # for PluginsSupport:
     setuptools >= 41.0