diff --git a/nova/api/openstack/placement/handlers/aggregate.py b/nova/api/openstack/placement/handlers/aggregate.py
index ed068b45ea89..a26839c3739d 100644
--- a/nova/api/openstack/placement/handlers/aggregate.py
+++ b/nova/api/openstack/placement/handlers/aggregate.py
@@ -122,7 +122,8 @@ def set_aggregates(req):
         if resource_provider.generation != rp_gen:
             raise webob.exc.HTTPConflict(
                 _("Resource provider's generation already changed. Please "
-                  "update the generation and try again."))
+                  "update the generation and try again."),
+                comment=errors.CONCURRENT_UPDATE)
         aggregate_uuids = data['aggregates']
     else:
         aggregate_uuids = data
diff --git a/nova/api/openstack/placement/handlers/inventory.py b/nova/api/openstack/placement/handlers/inventory.py
index 492d15697f8c..46135761568f 100644
--- a/nova/api/openstack/placement/handlers/inventory.py
+++ b/nova/api/openstack/placement/handlers/inventory.py
@@ -331,7 +331,8 @@ def set_inventories(req):
     data = _extract_inventories(req.body, schema.PUT_INVENTORY_SCHEMA)
     if data['resource_provider_generation'] != resource_provider.generation:
         raise webob.exc.HTTPConflict(
-            _('resource provider generation conflict'))
+            _('resource provider generation conflict'),
+            comment=errors.CONCURRENT_UPDATE)
 
     inv_list = []
     for res_class, inventory_data in data['inventories'].items():
@@ -436,7 +437,8 @@ def update_inventory(req):
     data = _extract_inventory(req.body, schema.BASE_INVENTORY_SCHEMA)
     if data['resource_provider_generation'] != resource_provider.generation:
         raise webob.exc.HTTPConflict(
-            _('resource provider generation conflict'))
+            _('resource provider generation conflict'),
+            comment=errors.CONCURRENT_UPDATE)
 
     inventory = _make_inventory_object(resource_provider,
                                        resource_class,
diff --git a/nova/api/openstack/placement/handlers/trait.py b/nova/api/openstack/placement/handlers/trait.py
index c5388f48eacc..b76907f1ad9f 100644
--- a/nova/api/openstack/placement/handlers/trait.py
+++ b/nova/api/openstack/placement/handlers/trait.py
@@ -226,7 +226,8 @@ def update_traits_for_resource_provider(req):
         raise webob.exc.HTTPConflict(
             _("Resource provider's generation already changed. Please update "
               "the generation and try again."),
-            json_formatter=util.json_error_formatter)
+            json_formatter=util.json_error_formatter,
+            comment=errors.CONCURRENT_UPDATE)
 
     trait_objs = rp_obj.TraitList.get_all(
         context, filters={'name_in': traits})
diff --git a/nova/api/openstack/placement/util.py b/nova/api/openstack/placement/util.py
index 4192673e2d36..be4607074808 100644
--- a/nova/api/openstack/placement/util.py
+++ b/nova/api/openstack/placement/util.py
@@ -639,7 +639,8 @@ def ensure_consumer(ctx, consumer_uuid, project_id, user_id,
                       {
                           'expected_gen': consumer.generation,
                           'got_gen': consumer_generation,
-                      })
+                      },
+                      comment=errors.CONCURRENT_UPDATE)
         # NOTE(jaypipes): The user may have specified a different project and
         # user external ID than the one that we had for the consumer. If this
         # is the case, go ahead and modify the consumer record with the
@@ -681,7 +682,8 @@ def ensure_consumer(ctx, consumer_uuid, project_id, user_id,
             if consumer_generation is not None:
                 raise webob.exc.HTTPConflict(
                     _('consumer generation conflict - '
-                      'expected null but got %s') % consumer_generation)
+                      'expected null but got %s') % consumer_generation,
+                    comment=errors.CONCURRENT_UPDATE)
         # No such consumer. This is common for new allocations. Create the
         # consumer record
         try:
diff --git a/nova/tests/functional/api/openstack/placement/gabbits/aggregate.yaml b/nova/tests/functional/api/openstack/placement/gabbits/aggregate.yaml
index 0d87a15d2459..fb75f9e7ae0e 100644
--- a/nova/tests/functional/api/openstack/placement/gabbits/aggregate.yaml
+++ b/nova/tests/functional/api/openstack/placement/gabbits/aggregate.yaml
@@ -116,6 +116,8 @@ tests:
       resource_provider_generation: 0
       aggregates: []
   status: 409
+  response_json_paths:
+      $.errors[0].code: placement.concurrent_update
 
 - name: clear those aggregates
   PUT: $LAST_URL
diff --git a/nova/tests/functional/api/openstack/placement/gabbits/allocations-1.28.yaml b/nova/tests/functional/api/openstack/placement/gabbits/allocations-1.28.yaml
index df8fadd66b72..77358836a560 100644
--- a/nova/tests/functional/api/openstack/placement/gabbits/allocations-1.28.yaml
+++ b/nova/tests/functional/api/openstack/placement/gabbits/allocations-1.28.yaml
@@ -64,6 +64,8 @@ tests:
   response_strings:
     - consumer generation conflict
     - expected null but got 5
+  response_json_paths:
+      $.errors[0].code: placement.concurrent_update
 
 - name: new version gen is None no existing
   PUT: /allocations/22222222-2222-2222-2222-222222222222
@@ -147,6 +149,8 @@ tests:
   status: 409
   response_strings:
     - consumer generation conflict
+  response_json_paths:
+      $.errors[0].code: placement.concurrent_update
 
 - name: old version no gen existing
   PUT: /allocations/44444444-4444-4444-4444-444444444444
diff --git a/nova/tests/functional/api/openstack/placement/gabbits/inventory.yaml b/nova/tests/functional/api/openstack/placement/gabbits/inventory.yaml
index 732f8a32ca79..6edff1f5dfcc 100644
--- a/nova/tests/functional/api/openstack/placement/gabbits/inventory.yaml
+++ b/nova/tests/functional/api/openstack/placement/gabbits/inventory.yaml
@@ -220,6 +220,7 @@ tests:
   PUT: $LAST_URL
   request_headers:
       content-type: application/json
+      openstack-api-version: placement 1.23
   data:
       resource_provider_generation: 5
       total: 2048
@@ -228,6 +229,7 @@ tests:
       - resource provider generation conflict
   response_json_paths:
       $.errors[0].title: Conflict
+      $.errors[0].code: placement.concurrent_update
 
 - name: modify inventory no such resource class in inventory
   PUT: /resource_providers/$ENVIRON['RP_UUID']/inventories/MEMORY_MB
@@ -467,6 +469,7 @@ tests:
   PUT: /resource_providers/$ENVIRON['RP_UUID']/inventories
   request_headers:
       content-type: application/json
+      openstack-api-version: placement 1.23
   data:
       resource_provider_generation: 99
       inventories:
@@ -477,6 +480,7 @@ tests:
       - resource provider generation conflict
   response_json_paths:
       $.errors[0].title: Conflict
+      $.errors[0].code: placement.concurrent_update
 
 - name: put all inventory unknown resource class
   PUT: /resource_providers/$ENVIRON['RP_UUID']/inventories
diff --git a/nova/tests/functional/api/openstack/placement/gabbits/traits.yaml b/nova/tests/functional/api/openstack/placement/gabbits/traits.yaml
index 6312a243dcd7..a5010d2cb4d4 100644
--- a/nova/tests/functional/api/openstack/placement/gabbits/traits.yaml
+++ b/nova/tests/functional/api/openstack/placement/gabbits/traits.yaml
@@ -325,6 +325,7 @@ tests:
   PUT: /resource_providers/$ENVIRON['RP_UUID']/traits
   request_headers:
     content-type: application/json
+    openstack-api-version: placement 1.23
   status: 409
   data:
     traits:
@@ -332,6 +333,8 @@ tests:
     resource_provider_generation: 5
   response_strings:
     - Resource provider's generation already changed. Please update the generation and try again.
+  response_json_paths:
+      $.errors[0].code: placement.concurrent_update
 
 - name: set non existed traits for resource provider
   PUT: /resource_providers/$ENVIRON['RP_UUID']/traits