diff --git a/mini-relay/app.py b/mini-relay/app.py
index a638b9d9..e03895ce 100644
--- a/mini-relay/app.py
+++ b/mini-relay/app.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import flask
 
 app = flask.Flask(__name__)
@@ -9,3 +11,11 @@ def envelope(p: str) -> flask.Response:
     ret = app.make_response(('', 204))
     ret.access_control_allow_origin = '*'
     return ret
+
+
+@app.post('/<path:path>')
+def unhandled(path: str) -> tuple[str, int]:
+    print('*' * 79)
+    print(f'unhandled path: {path}')
+    print('*' * 79)
+    return '', 400