diff --git a/output/openapi/elasticsearch-openapi.json b/output/openapi/elasticsearch-openapi.json
index 8626a3dcfa..a65925c176 100644
--- a/output/openapi/elasticsearch-openapi.json
+++ b/output/openapi/elasticsearch-openapi.json
@@ -21230,11 +21230,13 @@
                       "items": {
                         "$ref": "#/components/schemas/migration.post_feature_upgrade.MigrationFeature"
                       }
+                    },
+                    "reason": {
+                      "type": "string"
                     }
                   },
                   "required": [
-                    "accepted",
-                    "features"
+                    "accepted"
                   ]
                 },
                 "examples": {
diff --git a/output/schema/schema.json b/output/schema/schema.json
index 5bfb890461..96d50f95e9 100644
--- a/output/schema/schema.json
+++ b/output/schema/schema.json
@@ -167034,7 +167034,7 @@
           }
         }
       ],
-      "specLocation": "migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts#L27-L29"
+      "specLocation": "migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts#L28-L30"
     },
     {
       "kind": "request",
@@ -167077,7 +167077,7 @@
           },
           {
             "name": "features",
-            "required": true,
+            "required": false,
             "type": {
               "kind": "array_of",
               "value": {
@@ -167088,6 +167088,17 @@
                 }
               }
             }
+          },
+          {
+            "name": "reason",
+            "required": false,
+            "type": {
+              "kind": "instance_of",
+              "type": {
+                "name": "string",
+                "namespace": "_builtins"
+              }
+            }
           }
         ]
       },
@@ -167101,7 +167112,7 @@
         "name": "Response",
         "namespace": "migration.post_feature_upgrade"
       },
-      "specLocation": "migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts#L20-L25"
+      "specLocation": "migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts#L20-L26"
     },
     {
       "kind": "interface",
diff --git a/output/typescript/types.ts b/output/typescript/types.ts
index cd56dbc140..859503a05a 100644
--- a/output/typescript/types.ts
+++ b/output/typescript/types.ts
@@ -14823,7 +14823,8 @@ export interface MigrationPostFeatureUpgradeRequest extends RequestBase {
 
 export interface MigrationPostFeatureUpgradeResponse {
   accepted: boolean
-  features: MigrationPostFeatureUpgradeMigrationFeature[]
+  features?: MigrationPostFeatureUpgradeMigrationFeature[]
+  reason?: string
 }
 
 export interface MlAdaptiveAllocationsSettings {
diff --git a/specification/migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts b/specification/migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts
index 4007fd899b..6c5602ae30 100644
--- a/specification/migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts
+++ b/specification/migration/post_feature_upgrade/PostFeatureUpgradeResponse.ts
@@ -20,7 +20,8 @@
 export class Response {
   body: {
     accepted: boolean
-    features: MigrationFeature[]
+    features?: MigrationFeature[]
+    reason?: string
   }
 }