diff --git a/keystoneclient/auth/base.py b/keystoneclient/auth/base.py
index 27faa2abc..c1cf69e0d 100644
--- a/keystoneclient/auth/base.py
+++ b/keystoneclient/auth/base.py
@@ -12,6 +12,7 @@
 
 import os
 
+from keystoneauth1 import plugin
 import six
 import stevedore
 
@@ -21,7 +22,7 @@ from keystoneclient import exceptions
 # NOTE(jamielennox): The AUTH_INTERFACE is a special value that can be
 # requested from get_endpoint. If a plugin receives this as the value of
 # 'interface' it should return the initial URL that was passed to the plugin.
-AUTH_INTERFACE = object()
+AUTH_INTERFACE = plugin.AUTH_INTERFACE
 
 PLUGIN_NAMESPACE = 'keystoneclient.auth.plugin'
 IDENTITY_AUTH_HEADER_NAME = 'X-Auth-Token'
diff --git a/keystoneclient/discover.py b/keystoneclient/discover.py
index 62aec44d3..7bc9cbe7a 100644
--- a/keystoneclient/discover.py
+++ b/keystoneclient/discover.py
@@ -17,6 +17,7 @@ from debtcollector import removals
 import six
 
 from keystoneclient import _discover
+from keystoneclient.auth import base
 from keystoneclient import exceptions
 from keystoneclient.i18n import _
 from keystoneclient import session as client_session
@@ -170,11 +171,14 @@ class Discover(_discover.Discover):
         elif auth_url:
             self._use_endpoint = False
             url = auth_url
+        elif session.auth:
+            self._use_endpoint = False
+            url = session.get_endpoint(interface=base.AUTH_INTERFACE)
 
         if not url:
             raise exceptions.DiscoveryFailure(
-                _('Not enough information to determine URL. Provide either '
-                  'auth_url or endpoint'))
+                _('Not enough information to determine URL. Provide'
+                  ' either a Session, or auth_url or endpoint'))
 
         self._client_kwargs = kwargs
         super(Discover, self).__init__(session, url,
diff --git a/keystoneclient/tests/unit/auth/test_identity_v3.py b/keystoneclient/tests/unit/auth/test_identity_v3.py
index aaae50080..f0c36af50 100644
--- a/keystoneclient/tests/unit/auth/test_identity_v3.py
+++ b/keystoneclient/tests/unit/auth/test_identity_v3.py
@@ -216,7 +216,7 @@ class V3IdentityPlugin(utils.TestCase):
                         username=self.TEST_USER,
                         password=self.TEST_PASS)
         s = session.Session(auth=a)
-        cs = client.Client(session=s, auth_url=self.TEST_URL)
+        cs = client.Client(session=s)
 
         # As a sanity check on the auth_ref, make sure client has the
         # proper user id, that it fetches the right project response
diff --git a/requirements.txt b/requirements.txt
index 808053d2a..9f19ff994 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,6 +8,7 @@ argparse
 Babel>=1.3
 iso8601>=0.1.9
 debtcollector>=0.3.0 # Apache-2.0
+keystoneauth1>=1.0.0
 netaddr!=0.7.16,>=0.7.12
 oslo.config>=2.3.0 # Apache-2.0
 oslo.i18n>=1.5.0 # Apache-2.0