diff --git a/.changeset/four-ways-tap.md b/.changeset/four-ways-tap.md
new file mode 100644
index 000000000..89af56e0a
--- /dev/null
+++ b/.changeset/four-ways-tap.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes an issue that prevents importing `'astro/app'`
diff --git a/packages/astro/src/core/app/index.ts b/packages/astro/src/core/app/index.ts
index 288385598..da025609a 100644
--- a/packages/astro/src/core/app/index.ts
+++ b/packages/astro/src/core/app/index.ts
@@ -12,7 +12,7 @@ import { consoleLogDestination } from '../logger/console.js';
 import { error, type LogOptions } from '../logger/core.js';
 import { prependForwardSlash, removeTrailingForwardSlash } from '../path.js';
 import { RedirectSinglePageBuiltModule } from '../redirects/index.js';
-import { isResponse } from '../render/core';
+import { isResponse } from '../render/core.js';
 import {
 	createEnvironment,
 	createRenderContext,
diff --git a/packages/astro/test/import-app.test.js b/packages/astro/test/import-app.test.js
new file mode 100644
index 000000000..7ac536306
--- /dev/null
+++ b/packages/astro/test/import-app.test.js
@@ -0,0 +1,13 @@
+import { expect } from 'chai';
+
+describe('Import astro/app', async () => {
+
+	it('Successfully imports astro/app', async () => {
+		try {
+			await import('astro/app');
+			expect(true).to.be.true;
+		} catch (err) {
+			expect.fail(undefined, undefined, `Importing astro/app should not throw an error: ${err}`);
+		}
+	});
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 82c130ed9..3d66633af 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2721,6 +2721,12 @@ importers:
         specifier: ^10.15.1
         version: 10.15.1
 
+  packages/astro/test/fixtures/import-app:
+    dependencies:
+      astro:
+        specifier: workspace:*
+        version: link:../../..
+
   packages/astro/test/fixtures/import-ts-with-js:
     dependencies:
       astro: