diff --git a/aider/main.py b/aider/main.py
index fe4e8517c..fe0821d08 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -382,7 +382,7 @@ def main(argv=None, input=None, output=None, force_git_root=None):
     )
     other_group.add_argument(
         "--message-file",
-        "-mf",
+        "-f",
         metavar="MESSAGE_FILE",
         help="Specify a file containing the message to send GPT, process reply, then exit (disables chat mode)",
     )
@@ -571,8 +571,7 @@ def main(argv=None, input=None, output=None, force_git_root=None):
         coder.run(with_message=args.message)
     elif args.message_file:
         try:
-            with open(args.message_file, 'r', encoding='utf-8') as file:
-                message_from_file = file.read()
+            message_from_file = io.read_text(args.message_file)
             io.tool_output()
             coder.run(with_message=message_from_file)
         except FileNotFoundError:
diff --git a/tests/test_main.py b/tests/test_main.py
index fc363ce5f..b61de9d90 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -182,16 +182,15 @@ class TestMain(TestCase):
             _, kwargs = MockCoder.call_args
             assert kwargs["dirty_commits"] is True
 
-    @patch('aider.main.InputOutput.confirm_ask', return_value=True)
-    def test_message_file_flag(self, mock_confirm):
+    def test_message_file_flag(self):
         message_file_content = "This is a test message from a file."
-        message_file_path = "test_message.txt"
+        message_file_path = tempfile.mktemp()
         with open(message_file_path, 'w', encoding='utf-8') as message_file:
             message_file.write(message_file_content)
 
         with patch("aider.main.Coder.create") as MockCoder:
             MockCoder.return_value.run = MagicMock()
-            main(["--message-file", message_file_path], input=DummyInput(), output=DummyOutput())
+            main(["--yes", "--message-file", message_file_path], input=DummyInput(), output=DummyOutput())
             MockCoder.return_value.run.assert_called_once_with(with_message=message_file_content)
 
         os.remove(message_file_path)