diff --git a/glanceclient/shell.py b/glanceclient/shell.py
index ca103598..3a32bfb6 100644
--- a/glanceclient/shell.py
+++ b/glanceclient/shell.py
@@ -166,6 +166,8 @@ class OpenStackImagesShell(object):
         parser.add_argument('--os_image_api_version',
                             help=argparse.SUPPRESS)
 
+        parser.set_defaults(func=self.do_help)
+
         if osprofiler_profiler:
             parser.add_argument('--profile',
                                 metavar='HMAC_KEY',
diff --git a/glanceclient/tests/unit/test_shell.py b/glanceclient/tests/unit/test_shell.py
index 74d1c333..129b1275 100644
--- a/glanceclient/tests/unit/test_shell.py
+++ b/glanceclient/tests/unit/test_shell.py
@@ -211,6 +211,14 @@ class ShellTest(testutils.TestCase):
             self.assertEqual(0, actual)
             self.assertFalse(et_mock.called)
 
+    def test_help_no_subcommand(self):
+        shell = openstack_shell.OpenStackImagesShell()
+        argstr = '--os-image-api-version 2'
+        with mock.patch.object(shell, '_get_keystone_auth_plugin') as et_mock:
+            actual = shell.main(argstr.split())
+            self.assertEqual(0, actual)
+            self.assertFalse(et_mock.called)
+
     def test_blank_call(self):
         shell = openstack_shell.OpenStackImagesShell()
         with mock.patch.object(shell, '_get_keystone_auth_plugin') as et_mock:
diff --git a/releasenotes/notes/fix-undesirable-raw-python-error-66e3ddaca7b72ae2.yaml b/releasenotes/notes/fix-undesirable-raw-python-error-66e3ddaca7b72ae2.yaml
new file mode 100644
index 00000000..d6fad7d2
--- /dev/null
+++ b/releasenotes/notes/fix-undesirable-raw-python-error-66e3ddaca7b72ae2.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    `Bug #1903727 <https://bugs.launchpad.net/python-glanceclient/+bug/1903727>`_:
+    Fixed raw Python error message when using ``glance`` without
+    a subcommand while passing an optional argument, such as
+    ``--os-image-api-version``.