diff --git a/novaclient/client.py b/novaclient/client.py
index 3d95f57b8..441114185 100644
--- a/novaclient/client.py
+++ b/novaclient/client.py
@@ -825,6 +825,32 @@ def get_client_class(version):
     return client_class
 
 
+def _check_arguments(kwargs, release, deprecated_name, right_name=None):
+    """Process deprecation of arguments.
+
+    Checks presence of deprecated argument in kwargs, prints proper warning
+    message, renames key to right one it needed.
+    """
+    if deprecated_name in kwargs:
+        msg = _LW("The '%(old)s' argument is deprecated in %(release)s and "
+                  "its use may result in errors in future releases.") % {
+            "old": deprecated_name, "release": release}
+        if right_name:
+            if right_name in kwargs:
+                msg += _LW(" As '%(new)s' is provided, the '%(old)s' argument "
+                           "will be ignored.") % {"old": deprecated_name,
+                                                  "new": right_name}
+                kwargs.pop(deprecated_name)
+            else:
+                msg += _LW(" Use '%s' instead.") % right_name
+                kwargs[right_name] = kwargs.pop(deprecated_name)
+        else:
+            # just ignore it
+            kwargs.pop(deprecated_name)
+
+        warnings.warn(msg)
+
+
 def Client(version, username=None, api_key=None, project_id=None,
            auth_url=None, **kwargs):
     """Initialize client object based on given version.
@@ -847,6 +873,10 @@ def Client(version, username=None, api_key=None, project_id=None,
     session API. See "The novaclient Python API" page at
     python-novaclient's doc.
     """
+
+    _check_arguments(kwargs, "Ocata", "auth_plugin")
+    _check_arguments(kwargs, "Ocata", "auth_system")
+
     api_version, client_class = _get_client_class_and_version(version)
     kwargs.pop("direct_use", None)
     return client_class(username=username, api_key=api_key,
diff --git a/novaclient/tests/unit/test_client.py b/novaclient/tests/unit/test_client.py
index 9a0616c25..b559882fe 100644
--- a/novaclient/tests/unit/test_client.py
+++ b/novaclient/tests/unit/test_client.py
@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-
+import copy
 import logging
 
 import fixtures
@@ -478,16 +478,16 @@ class SessionClientTest(utils.TestCase):
                                                     'compute')
 
 
-class DiscoverExtensionTest(utils.TestCase):
+class ClientsUtilsTest(utils.TestCase):
 
     @mock.patch("novaclient.client._discover_via_entry_points")
     @mock.patch("novaclient.client._discover_via_contrib_path")
     @mock.patch("novaclient.client._discover_via_python_path")
     @mock.patch("novaclient.extension.Extension")
-    def test_discover_all(self, mock_extension,
-                          mock_discover_via_python_path,
-                          mock_discover_via_contrib_path,
-                          mock_discover_via_entry_points):
+    def test_discover_extensions_all(self, mock_extension,
+                                     mock_discover_via_python_path,
+                                     mock_discover_via_contrib_path,
+                                     mock_discover_via_entry_points):
         def make_gen(start, end):
             def f(*args, **kwargs):
                 for i in range(start, end):
@@ -513,10 +513,9 @@ class DiscoverExtensionTest(utils.TestCase):
     @mock.patch("novaclient.client._discover_via_contrib_path")
     @mock.patch("novaclient.client._discover_via_python_path")
     @mock.patch("novaclient.extension.Extension")
-    def test_discover_only_contrib(self, mock_extension,
-                                   mock_discover_via_python_path,
-                                   mock_discover_via_contrib_path,
-                                   mock_discover_via_entry_points):
+    def test_discover_extensions_only_contrib(
+            self, mock_extension, mock_discover_via_python_path,
+            mock_discover_via_contrib_path, mock_discover_via_entry_points):
         mock_discover_via_contrib_path.return_value = [("name", "module")]
 
         version = novaclient.api_versions.APIVersion("2.0")
@@ -526,3 +525,39 @@ class DiscoverExtensionTest(utils.TestCase):
         self.assertFalse(mock_discover_via_python_path.called)
         self.assertFalse(mock_discover_via_entry_points.called)
         mock_extension.assert_called_once_with("name", "module")
+
+    @mock.patch("novaclient.client.warnings")
+    def test__check_arguments(self, mock_warnings):
+        release = "Coolest"
+
+        # no reference
+        novaclient.client._check_arguments({}, release=release,
+                                           deprecated_name="foo")
+        self.assertFalse(mock_warnings.warn.called)
+        novaclient.client._check_arguments({}, release=release,
+                                           deprecated_name="foo",
+                                           right_name="bar")
+        self.assertFalse(mock_warnings.warn.called)
+
+        # with alternative
+        original_kwargs = {"foo": "text"}
+        actual_kwargs = copy.copy(original_kwargs)
+        self.assertEqual(original_kwargs, actual_kwargs)
+        novaclient.client._check_arguments(actual_kwargs, release=release,
+                                           deprecated_name="foo",
+                                           right_name="bar")
+        self.assertNotEqual(original_kwargs, actual_kwargs)
+        self.assertEqual({"bar": original_kwargs["foo"]}, actual_kwargs)
+        self.assertTrue(mock_warnings.warn.called)
+
+        mock_warnings.warn.reset_mock()
+
+        # without alternative
+        original_kwargs = {"foo": "text"}
+        actual_kwargs = copy.copy(original_kwargs)
+        self.assertEqual(original_kwargs, actual_kwargs)
+        novaclient.client._check_arguments(actual_kwargs, release=release,
+                                           deprecated_name="foo")
+        self.assertNotEqual(original_kwargs, actual_kwargs)
+        self.assertEqual({}, actual_kwargs)
+        self.assertTrue(mock_warnings.warn.called)