diff --git a/os_client_config/cloud_config.py b/os_client_config/cloud_config.py
index 0860924..fec3500 100644
--- a/os_client_config/cloud_config.py
+++ b/os_client_config/cloud_config.py
@@ -215,14 +215,20 @@ class CloudConfig(object):
             requestsexceptions.squelch_warnings(insecure_requests=not verify)
             self._keystone_session = self._session_constructor(
                 auth=self._auth,
-                app_name=self._app_name,
-                app_version=self._app_version,
                 verify=verify,
                 cert=cert,
                 timeout=self.config['api_timeout'])
             if hasattr(self._keystone_session, 'additional_user_agent'):
                 self._keystone_session.additional_user_agent.append(
                     ('os-client-config', os_client_config.__version__))
+            # Using old keystoneauth with new os-client-config fails if
+            # we pass in app_name and app_version. Those are not essential,
+            # nor a reason to bump our minimum, so just test for the session
+            # having the attribute post creation and set them then.
+            if hasattr(self._keystone_session, 'app_name'):
+                self._keystone_session.app_name = self._app_name
+            if hasattr(self._keystone_session, 'app_version'):
+                self._keystone_session.app_version = self._app_version
         return self._keystone_session
 
     def get_session_client(self, service_key):
diff --git a/os_client_config/tests/test_cloud_config.py b/os_client_config/tests/test_cloud_config.py
index 0671fcc..5df1faf 100644
--- a/os_client_config/tests/test_cloud_config.py
+++ b/os_client_config/tests/test_cloud_config.py
@@ -187,8 +187,29 @@ class TestCloudConfig(base.TestCase):
         cc.get_session()
         mock_session.assert_called_with(
             auth=mock.ANY,
-            verify=True, cert=None, timeout=None,
-            app_name=None, app_version=None)
+            verify=True, cert=None, timeout=None)
+        self.assertEqual(
+            fake_session.additional_user_agent,
+            [('os-client-config', '1.2.3')])
+
+    @mock.patch.object(ksa_session, 'Session')
+    def test_get_session_with_app_name(self, mock_session):
+        config_dict = defaults.get_defaults()
+        config_dict.update(fake_services_dict)
+        fake_session = mock.Mock()
+        fake_session.additional_user_agent = []
+        fake_session.app_name = None
+        fake_session.app_version = None
+        mock_session.return_value = fake_session
+        cc = cloud_config.CloudConfig(
+            "test1", "region-al", config_dict, auth_plugin=mock.Mock(),
+            app_name="test_app", app_version="test_version")
+        cc.get_session()
+        mock_session.assert_called_with(
+            auth=mock.ANY,
+            verify=True, cert=None, timeout=None)
+        self.assertEqual(fake_session.app_name, "test_app")
+        self.assertEqual(fake_session.app_version, "test_version")
         self.assertEqual(
             fake_session.additional_user_agent,
             [('os-client-config', '1.2.3')])
@@ -206,8 +227,7 @@ class TestCloudConfig(base.TestCase):
         cc.get_session()
         mock_session.assert_called_with(
             auth=mock.ANY,
-            verify=True, cert=None, timeout=9,
-            app_name=None, app_version=None)
+            verify=True, cert=None, timeout=9)
         self.assertEqual(
             fake_session.additional_user_agent,
             [('os-client-config', '1.2.3')])
diff --git a/releasenotes/notes/fix-compat-with-old-keystoneauth-66e11ee9d008b962.yaml b/releasenotes/notes/fix-compat-with-old-keystoneauth-66e11ee9d008b962.yaml
new file mode 100644
index 0000000..80d09fb
--- /dev/null
+++ b/releasenotes/notes/fix-compat-with-old-keystoneauth-66e11ee9d008b962.yaml
@@ -0,0 +1,7 @@
+---
+issues:
+  - Fixed a regression when using latest os-client-config with
+    the keystoneauth from stable/newton. Although this isn't a
+    super common combination, the added feature that broke the
+    interaction is really not worthy of the incompatibility, so
+    a workaround was added.