diff --git a/novaclient/client.py b/novaclient/client.py
index 5fa7060dd..f2143d685 100644
--- a/novaclient/client.py
+++ b/novaclient/client.py
@@ -809,7 +809,8 @@ def get_client_class(version):
     return client_class
 
 
-def Client(version, *args, **kwargs):
+def Client(version, username=None, api_key=None, project_id=None,
+           auth_url=None, *args, **kwargs):
     """Initialize client object based on given version.
 
     HOW-TO:
@@ -830,7 +831,15 @@ def Client(version, *args, **kwargs):
     session API. See "The novaclient Python API" page at
     python-novaclient's doc.
     """
+    if args:
+        warnings.warn("Only VERSION, USERNAME, PASSWORD, PROJECT_ID and "
+                      "AUTH_URL arguments can be specified as positional "
+                      "arguments. All other variables should be keyword "
+                      "arguments. Note that this will become an error in "
+                      "Ocata.")
     api_version, client_class = _get_client_class_and_version(version)
     kwargs.pop("direct_use", None)
-    return client_class(api_version=api_version, direct_use=False,
+    return client_class(username=username, api_key=api_key,
+                        project_id=project_id, auth_url=auth_url,
+                        api_version=api_version, direct_use=False,
                         *args, **kwargs)