diff --git a/pargv.py b/pargv.py
index 71f189d..1c2753b 100644
--- a/pargv.py
+++ b/pargv.py
@@ -12,7 +12,7 @@ def parse_args(argv=None):
     for arg in argv:
         if arg.startswith('-'):
             break
-        args.append(arg)
+        args.append(arg.replace('-', '_'))
     argv = argv[len(args):]
 
     kwargs = {}
diff --git a/tests/test_functionality.py b/tests/test_functionality.py
index 3f4fd1f..b77d422 100644
--- a/tests/test_functionality.py
+++ b/tests/test_functionality.py
@@ -29,6 +29,12 @@ def test_single_positional_argument():
     assert kwargs == {}
 
 
+def test_single_positional_argument_with_underscore():
+    args, kwargs = parse_args(['the-app'])
+    assert args == ['the_app']
+    assert kwargs == {}
+
+
 def test_positional_arguments():
     args, kwargs = parse_args(['app', 'command'])
     assert args == ['app', 'command']