diff --git a/keystone/federation/utils.py b/keystone/federation/utils.py
index 48ae6b3d49..409d9625b2 100644
--- a/keystone/federation/utils.py
+++ b/keystone/federation/utils.py
@@ -412,8 +412,8 @@ def transform_to_group_ids(group_names, mapping_id,
                 group['name'], resolve_domain(group['domain']))
             yield group_dict['id']
         except exception.GroupNotFound:
-            raise exception.MappedGroupNotFound(group_id=group['name'],
-                                                mapping_id=mapping_id)
+            LOG.debug('Group %s has no entry in the backend',
+                      group['name'])
 
 
 def get_assertion_params_from_env(request):
diff --git a/keystone/tests/unit/test_v3_federation.py b/keystone/tests/unit/test_v3_federation.py
index 92689582e8..0fc49ce4ed 100644
--- a/keystone/tests/unit/test_v3_federation.py
+++ b/keystone/tests/unit/test_v3_federation.py
@@ -1948,9 +1948,8 @@ class FederatedTokenTests(test_v3.RestfulTestCase, FederatedSetupMixin):
         self.assertEqual(ref_groups, token_groups)
 
     def test_issue_unscoped_tokens_nonexisting_group(self):
-        self.assertRaises(exception.MappedGroupNotFound,
-                          self._issue_unscoped_token,
-                          assertion='ANOTHER_TESTER_ASSERTION')
+        r = self._issue_unscoped_token(assertion='ANOTHER_TESTER_ASSERTION')
+        self.assertIsNotNone(r.headers.get('X-Subject-Token'))
 
     def test_issue_unscoped_token_with_remote_no_attribute(self):
         r = self._issue_unscoped_token(idp=self.IDP_WITH_REMOTE,
@@ -2498,6 +2497,10 @@ class FederatedTokenTests(test_v3.RestfulTestCase, FederatedSetupMixin):
             ]
         }
         PROVIDERS.federation_api.update_mapping(self.mapping['id'], rules)
+        r = self._issue_unscoped_token(assertion='UNMATCHED_GROUP_ASSERTION')
+        assigned_group_ids = r.json['token']['user']['OS-FEDERATION']['groups']
+        self.assertEqual(1, len(assigned_group_ids))
+        self.assertEqual(group['id'], assigned_group_ids[0]['id'])
 
     def test_empty_blacklist_passess_all_values(self):
         """Test a mapping with empty blacklist specified.