diff --git a/x-pack/plugins/upgrade_assistant/common/types.ts b/x-pack/plugins/upgrade_assistant/common/types.ts
index 5fb1cc8e0372f3..9bcbf629a88f64 100644
--- a/x-pack/plugins/upgrade_assistant/common/types.ts
+++ b/x-pack/plugins/upgrade_assistant/common/types.ts
@@ -240,7 +240,7 @@ export interface SystemIndicesUpgradeFeature {
   upgrade_status: UPGRADE_STATUS;
   indices: Array<{
     index: string;
-    index_version: string;
+    version: string;
   }>;
 }
 export interface SystemIndicesUpgradeStatus {
diff --git a/x-pack/plugins/upgrade_assistant/server/lib/es_system_indices_upgrade.test.ts b/x-pack/plugins/upgrade_assistant/server/lib/es_system_indices_upgrade.test.ts
new file mode 100644
index 00000000000000..8010d7ff7acfaf
--- /dev/null
+++ b/x-pack/plugins/upgrade_assistant/server/lib/es_system_indices_upgrade.test.ts
@@ -0,0 +1,53 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { convertFeaturesListToArray } from './es_system_indices_upgrade';
+import { SystemIndicesUpgradeStatus } from '../../common/types';
+
+const esUpgradeSystemIndicesStatusMock: SystemIndicesUpgradeStatus = {
+  features: [
+    {
+      feature_name: 'machine_learning',
+      minimum_index_version: '7.1.1',
+      upgrade_status: 'UPGRADE_NEEDED',
+      indices: [
+        {
+          index: '.ml-config',
+          version: '7.1.1',
+        },
+        {
+          index: '.ml-notifications',
+          version: '7.1.1',
+        },
+      ],
+    },
+    {
+      feature_name: 'security',
+      minimum_index_version: '7.1.1',
+      upgrade_status: 'UPGRADE_NEEDED',
+      indices: [
+        {
+          index: '.ml-config',
+          version: '7.1.1',
+        },
+      ],
+    },
+  ],
+  upgrade_status: 'UPGRADE_NEEDED',
+};
+
+describe('convertFeaturesListToArray', () => {
+  it('converts list with features to flat array of uniq indices', async () => {
+    const result = convertFeaturesListToArray(esUpgradeSystemIndicesStatusMock.features);
+    expect(result).toEqual(['.ml-config', '.ml-notifications']);
+  });
+
+  it('returns empty array if no features are passed to it', async () => {
+    const result = convertFeaturesListToArray([]);
+    expect(result).toEqual([]);
+  });
+});