diff --git a/setup.py b/setup.py
index fd32240..db341a9 100644
--- a/setup.py
+++ b/setup.py
@@ -23,6 +23,7 @@
     "jsonref",
     "ipython",
     "flatterer",
+    "Werkzeug<3",
     "frozen-flask",
     "bootstrap-flask",
     "markdown",