diff --git a/swh/objstorage/tests/server_testing.py b/swh/objstorage/tests/server_testing.py
--- a/swh/objstorage/tests/server_testing.py
+++ b/swh/objstorage/tests/server_testing.py
@@ -56,7 +56,7 @@
 
         # Worker function for multiprocessing
         def worker(app, port):
-            return aiohttp.web.run_app(app, port=port, print=(lambda _: None))
+            return aiohttp.web.run_app(app, port=port, print=lambda *_: None)
 
         self.process = multiprocessing.Process(
             target=worker, args=(self.app, self.port)