diff --git a/packages/frontend-defaults/src/createApp.test.tsx b/packages/frontend-defaults/src/createApp.test.tsx
index 5b5e6b0e29..af8517624a 100644
--- a/packages/frontend-defaults/src/createApp.test.tsx
+++ b/packages/frontend-defaults/src/createApp.test.tsx
@@ -386,40 +386,6 @@ describe('createApp', () => {
     ).resolves.toBeInTheDocument();
   });
 
-  it('should allow unknown extension config if the flag is set', async () => {
-    const app = createApp({
-      features: [
-        appPlugin,
-        createFrontendPlugin({
-          pluginId: 'test',
-          extensions: [
-            PageBlueprint.make({
-              params: {
-                path: '/',
-                loader: async () => <div>Derp</div>,
-              },
-            }),
-          ],
-        }),
-      ],
-      advanced: {
-        allowUnknownExtensionConfig: true,
-        configLoader: async () => ({
-          config: mockApis.config({
-            data: {
-              app: {
-                extensions: [{ 'unknown:lols/wut': false }],
-              },
-            },
-          }),
-        }),
-      },
-    });
-
-    await renderWithEffects(app.createRoot());
-
-    await expect(screen.findByText('Derp')).resolves.toBeInTheDocument();
-  });
   it('should make the app structure available through the AppTreeApi', async () => {
     let appTreeApi: AppTreeApi | undefined = undefined;
 
diff --git a/packages/frontend-defaults/src/createApp.tsx b/packages/frontend-defaults/src/createApp.tsx
index bd1311740b..c4cf43fb2e 100644
--- a/packages/frontend-defaults/src/createApp.tsx
+++ b/packages/frontend-defaults/src/createApp.tsx
@@ -59,17 +59,6 @@ export interface CreateAppOptions {
    * Advanced, more rarely used options.
    */
   advanced?: {
-    /**
-     * If set to true, the system will silently accept and move on if
-     * encountering config for extensions that do not exist. The default is to
-     * reject such config to help catch simple mistakes.
-     *
-     * This flag can be useful in some scenarios where you have a dynamic set of
-     * extensions enabled at different times, but also increases the risk of
-     * accidentally missing e.g. simple typos in your config.
-     */
-    allowUnknownExtensionConfig?: boolean;
-
     /**
      * Sets a custom config loader, replacing the builtin one.
      *