diff --git a/slugify/__main__.py b/slugify/__main__.py
index fde2a86..b740db1 100644
--- a/slugify/__main__.py
+++ b/slugify/__main__.py
@@ -25,9 +25,9 @@ def parse_args(argv: list[str]) -> argparse.Namespace:
     parser.add_argument("--max-length", type=int, default=0,
                         help="Output string length, 0 for no limit")
     parser.add_argument("--word-boundary", action='store_true', default=False,
-                        help="Truncate to complete word even if length ends up shorter than --max_length")
+                        help="Truncate to complete word even if length ends up shorter than --max-length")
     parser.add_argument("--save-order", action='store_true', default=False,
-                        help="When set and --max_length > 0 return whole words in the initial order")
+                        help="When set and --max-length > 0 return whole words in the initial order")
     parser.add_argument("--separator", type=str, default=DEFAULT_SEPARATOR,
                         help="Separator between words. By default " + DEFAULT_SEPARATOR)
     parser.add_argument("--stopwords", nargs='+',
diff --git a/tests/test_cli_interrupt.py b/tests/test_cli_interrupt.py
index eda9337..463cb0f 100644
--- a/tests/test_cli_interrupt.py
+++ b/tests/test_cli_interrupt.py
@@ -21,3 +21,11 @@ def test_keyboard_interrupt_exits_without_traceback(capsys):
     captured = capsys.readouterr()
     assert captured.out == ''
     assert captured.err == ''
+
+
+def test_help_uses_hyphenated_max_length(capsys):
+    with pytest.raises(SystemExit):
+        cli.main(['slugify', '--help'])
+    out = capsys.readouterr().out
+    assert '--max_length' not in out
+    assert '--max-length' in out