diff --git a/tests/test_commands.py b/tests/test_commands.py
index 8eb6dcd61..fdbf91da5 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -9,7 +9,7 @@ from aider.coder import Coder
 class TestCommands(unittest.TestCase):
     def test_cmd_add(self):
         with tempfile.TemporaryDirectory() as tmpdir:
-            io = IO(pretty=False, yes=True, input_history_file=None, chat_history_file=None)
+            io = IO(pretty=False, yes=True, input_history_file="", chat_history_file="")
             coder = Coder(root=tmpdir)
             commands = Commands(io, coder)