diff --git a/neutron/db/db_base_plugin_v2.py b/neutron/db/db_base_plugin_v2.py
index ac7010a9787..98a7997a20a 100644
--- a/neutron/db/db_base_plugin_v2.py
+++ b/neutron/db/db_base_plugin_v2.py
@@ -937,8 +937,8 @@ class NeutronDbPluginV2(db_base_plugin_common.DbBasePluginCommon,
                         self, **kwargs)
 
         with db_api.CONTEXT_WRITER.using(context):
-            subnet, changes = self.ipam.update_db_subnet(context, id, s,
-                                                         db_pools)
+            subnet, changes = self.ipam.update_db_subnet(
+                context, id, s, db_pools, subnet_obj=subnet_obj)
         return self._make_subnet_dict(subnet, context=context), orig
 
     @property
diff --git a/neutron/db/ipam_backend_mixin.py b/neutron/db/ipam_backend_mixin.py
index 34c785e6c0b..8148f8700bd 100644
--- a/neutron/db/ipam_backend_mixin.py
+++ b/neutron/db/ipam_backend_mixin.py
@@ -196,7 +196,8 @@ class IpamBackendMixin(db_base_plugin_common.DbBasePluginCommon):
             new_type.create()
         return updated_types
 
-    def update_db_subnet(self, context, subnet_id, s, oldpools):
+    def update_db_subnet(self, context, subnet_id, s, oldpools,
+            subnet_obj=None):
         changes = {}
         if "dns_nameservers" in s:
             changes['dns_nameservers'] = (
@@ -214,7 +215,7 @@ class IpamBackendMixin(db_base_plugin_common.DbBasePluginCommon):
             changes['service_types'] = (
                 self._update_subnet_service_types(context, subnet_id, s))
 
-        subnet_obj = self._get_subnet_object(context, subnet_id)
+        subnet_obj = subnet_obj or self._get_subnet_object(context, subnet_id)
         subnet_obj.update_fields(s)
         subnet_obj.update()
         return subnet_obj, changes
diff --git a/neutron/db/ipam_pluggable_backend.py b/neutron/db/ipam_pluggable_backend.py
index 6c379a1c74f..f1dc7e005df 100644
--- a/neutron/db/ipam_pluggable_backend.py
+++ b/neutron/db/ipam_pluggable_backend.py
@@ -494,8 +494,8 @@ class IpamPluggableBackend(ipam_backend_mixin.IpamBackendMixin):
         self._ipam_deallocate_ips(context, ipam_driver, port,
                                   port['fixed_ips'])
 
-    def update_db_subnet(self, context, id, s, old_pools):
-        subnet = obj_subnet.Subnet.get_object(context, id=id)
+    def update_db_subnet(self, context, id, s, old_pools, subnet_obj=None):
+        subnet = subnet_obj or obj_subnet.Subnet.get_object(context, id=id)
         old_segment_id = subnet.segment_id if subnet else None
         if 'segment_id' in s:
             self._validate_segment(
@@ -506,7 +506,7 @@ class IpamPluggableBackend(ipam_backend_mixin.IpamBackendMixin):
         # so create unchanged copy for ipam driver
         subnet_copy = copy.deepcopy(s)
         subnet, changes = super(IpamPluggableBackend, self).update_db_subnet(
-            context, id, s, old_pools)
+            context, id, s, old_pools, subnet_obj=subnet_obj)
         ipam_driver = driver.Pool.get_instance(None, context)
 
         # Set old allocation pools if no new pools are provided by user.