diff --git a/tempest/api/network/base_routers.py b/tempest/api/network/base_routers.py
index 5fb5232..f6fd871 100644
--- a/tempest/api/network/base_routers.py
+++ b/tempest/api/network/base_routers.py
@@ -38,10 +38,8 @@
         client.delete_router(router_id)
         # Asserting that the router is not found in the list
         # after deletion
-        list_body = self.routers_client.list_routers()
-        routers_list = list()
-        for router in list_body['routers']:
-            routers_list.append(router['id'])
+        list_body = client.list_routers()
+        routers_list = [router['id'] for router in list_body['routers']]
         self.assertNotIn(router_id, routers_list)
 
     def _add_router_interface_with_subnet_id(self, router_id, subnet_id):
diff --git a/tempest/lib/api_schema/response/compute/v2_1/availability_zone.py b/tempest/lib/api_schema/response/compute/v2_1/availability_zone.py
index f7b77a1..0dc28c3 100644
--- a/tempest/lib/api_schema/response/compute/v2_1/availability_zone.py
+++ b/tempest/lib/api_schema/response/compute/v2_1/availability_zone.py
@@ -51,7 +51,7 @@
 }
 
 detail = {
-    'type': 'object',
+    'type': ['object', 'null'],
     'patternProperties': {
         # NOTE: Here is for a hostname
         '^[a-zA-Z0-9-_.]+$': {
diff --git a/tempest/scenario/test_network_basic_ops.py b/tempest/scenario/test_network_basic_ops.py
index c324261..69b5250 100644
--- a/tempest/scenario/test_network_basic_ops.py
+++ b/tempest/scenario/test_network_basic_ops.py
@@ -321,11 +321,8 @@
         # We ping the external IP from the instance using its floating IP
         # which is always IPv4, so we must only test connectivity to
         # external IPv4 IPs if the external network is dualstack.
-        ext_ips = self.router['external_gateway_info']['external_fixed_ips']
-        subnet_ids = [sub['subnet_id'] for sub in ext_ips]
         v4_subnets = [s for s in self._list_subnets(
-            network_id=CONF.network.public_network_id)
-            if s['ip_version'] == 4 and s['id'] in subnet_ids]
+            network_id=CONF.network.public_network_id) if s['ip_version'] == 4]
         self.assertEqual(1, len(v4_subnets),
                          "Found %d IPv4 subnets" % len(v4_subnets))