diff --git a/setup.py b/setup.py
index fa07a0f..1ae3344 100644
--- a/setup.py
+++ b/setup.py
@@ -94,6 +94,7 @@ setup(
         'idna<3,>=2.5',
         # 7.x will be a major change.
         'mitmproxy>=8.0.0,<8.1',
+        'Werkzeug<3.0',
         # For REPLs
         'ptpython<4.0',
         # JP2 codec