diff --git a/neutron_tempest_plugin/api/base.py b/neutron_tempest_plugin/api/base.py
index c4bc71d..028d901 100644
--- a/neutron_tempest_plugin/api/base.py
+++ b/neutron_tempest_plugin/api/base.py
@@ -431,6 +431,8 @@
                 ip_version=ip_version, cidr=cidr, mask_bits=mask_bits):
             if gateway is not None:
                 kwargs['gateway_ip'] = str(gateway or (subnet_cidr.ip + 1))
+            else:
+                kwargs['gateway_ip'] = None
             try:
                 body = client.create_subnet(
                     network_id=network['id'],