diff --git a/swauth/middleware.py b/swauth/middleware.py
index 0bf6c6d..3fd5316 100644
--- a/swauth/middleware.py
+++ b/swauth/middleware.py
@@ -344,8 +344,16 @@ class Swauth(object):
             env['PATH_INFO'] = path.replace("%s:%s" % (account, user),
                                             account_id, 1)
             detail = json.loads(resp.body)
+            if detail:
+                creds = detail.get('auth')
+                try:
+                    auth_encoder, creds_dict = \
+                        swauth.authtypes.validate_creds(creds)
+                except ValueError as e:
+                    self.logger.error('%s' % e.args[0])
+                    return None
 
-            password = detail['auth'].split(':')[-1]
+            password = creds_dict['hash']
             msg = base64.urlsafe_b64decode(unquote(token))
 
             # https://bugs.python.org/issue5285
diff --git a/test/unit/test_middleware.py b/test/unit/test_middleware.py
index af8218c..1ed3314 100644
--- a/test/unit/test_middleware.py
+++ b/test/unit/test_middleware.py
@@ -14,6 +14,7 @@
 # limitations under the License.
 
 from contextlib import contextmanager
+import hashlib
 import json
 import mock
 from time import time
@@ -4062,6 +4063,29 @@ class TestAuth(unittest.TestCase):
                 'ozNCArMDAwMAovY29udGFpbmVyMw=='
         self.assertEqual(self.test_auth.get_groups(env, token), None)
 
+    def test_s3_only_hash_passed_to_hmac(self):
+        key = 'dadada'
+        salt = 'zuck'
+        key_hash = hashlib.sha1('%s%s' % (salt, key)).hexdigest()
+        auth_stored = "sha1:%s$%s" % (salt, key_hash)
+        self.test_auth.app = FakeApp(iter([
+            ('200 Ok', {},
+             json.dumps({"auth": auth_stored,
+                         "groups": [{'name': "act:usr"}, {'name': "act"},
+                                    {'name': ".admin"}]})),
+            ('204 Ok', {'X-Container-Meta-Account-Id': 'AUTH_act'}, '')]))
+        env = \
+            {'HTTP_AUTHORIZATION': 'AWS act:user:whatever',
+             'PATH_INFO': '/v1/AUTH_act/c1'}
+        token = 'UFVUCgoKRnJpLCAyNiBGZWIgMjAxNiAwNjo0NT'\
+                'ozNCArMDAwMAovY29udGFpbmVyMw=='
+        mock_hmac_new = mock.MagicMock()
+        with mock.patch('hmac.new', mock_hmac_new):
+            self.test_auth.get_groups(env, token)
+        self.assertTrue(mock_hmac_new.called)
+        # Assert that string passed to hmac.new is only the hash
+        self.assertEqual(mock_hmac_new.call_args[0][0], key_hash)
+
 
 if __name__ == '__main__':
     unittest.main()