nextjs - 💡(How to fix) Fix Turbopack 16.2.0 regression: app/icon.tsx returning Response.redirect() + firebase-admin import + next-intl crashes build with "Cannot read properties of undefined (reading 'default')" [2 comments, 2 participants]

Mrelijman · 2026-03-20T10:30:48Z

[nextjs] Link to the code that reproduces this issue https://github.com/Mrelijman/next16.2bug/tree/main/my-next-issue To Reproduce 1. Clone https://github.com/… ## Fix / Workaround All three must be present. Removing any one of them makes the build succeed. **Workaround:** Convert app/icon.tsx to a proper route handler at app/icon/route.ts with a GET() function instead of a default export. ### Link to the code that reproduces this issue https://github.com/Mrelijman/next16.2bug/tree/main/my-next-issue ### To Reproduce 1. Clone https://github.com/Mrelijman/next16.2bug/tree/main/my-next-issue 2. Run npm install 3. Run npm run build Build will fail with: TypeError: Cannot read properties of undefined (reading 'default') at Array.map at .next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053 ### Current vs. Expected behavior **Current**: Turbopack build fails during static page prerendering with: ``` TypeError: Cannot read properties of undefined (reading 'default') at (.next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053) at Array.map ( ) at aW (...js:6:1031) at aX (...js:6:1248) at aY (...js:6:1613) ``` **Expected**: Build succeeds, as it did on Next.js 16.1.7 with identical code. The crash happens inside Next.js's own bundled SSR chunk, not in user code. **The three ingredients required to reproduce:** 1. app/icon.tsx that returns Response.redirect() as default export 2. import 'firebase-admin/app' anywhere in icon.tsx 3. next-intl plugin wrapping the Next.js config + a rewrite pointing favicon.ico → /icon All three must be present. Removing any one of them makes the build succeed. **Workaround:** Convert app/icon.tsx to a proper route handler at app/icon/route.ts with a GET() function instead of a default export. ### Provide environment information ```bash Operating System: Platform: win32 Arch: x64 Version: Windows Server 2022 Standard Binaries: Node: 24.11.1 npm: 11.11.1 Relevant Packages: next: 16.2.0 react: 19.1.0 react-dom: 19.1.0 typescript: 5.9.3 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Turbopack ### Which stage(s) are affected? (Select all that apply) next build (local) ### Additional context - next build --webpack succeeds on 16.2.0 — Turbopack specific - next@16.1.7 with identical code builds fine — clean regression - On Windows there is no stack trace, just a digest, making this extremely hard to diagnose. The error points to /_not-found in the real project (not the actual icon.tsx file), sending debugging in completely the wrong direction - Took several hours to isolate because the error message is totally misleading - Tested next@16.2.1-canary.2 — still fails, suggesting not yet fixed

nextjs2026-03-20 10:30:48

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vercel/next.js#91706•Fetched 2026-04-08 01:02:22

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Error Message

TypeError: Cannot read properties of undefined (reading 'default') at <unknown> (.next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053) at Array.map (<anonymous>) at aW (...js:6:1031) at aX (...js:6:1248) at aY (...js:6:1613)

Root Cause

next build --webpack succeeds on 16.2.0 — Turbopack specific
[email protected] with identical code builds fine — clean regression
On Windows there is no stack trace, just a digest, making this extremely hard to diagnose. The error points to /_not-found in the real project (not the actual icon.tsx file), sending debugging in completely the wrong direction
Took several hours to isolate because the error message is totally misleading
Tested [email protected] — still fails, suggesting not yet fixed

Fix Action

Fix / Workaround

All three must be present. Removing any one of them makes the build succeed. Workaround: Convert app/icon.tsx to a proper route handler at app/icon/route.ts with a GET() function instead of a default export.

Code Example

TypeError: Cannot read properties of undefined (reading 'default')
    at <unknown> (.next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053)
    at Array.map (<anonymous>)
    at aW (...js:6:1031)
    at aX (...js:6:1248)
    at aY (...js:6:1613)

---

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows Server 2022 Standard
Binaries:
  Node: 24.11.1
  npm: 11.11.1
Relevant Packages:
  next: 16.2.0
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.9.3
Next.js Config:
  output: N/A

RAW_BUFFERClick to expand / collapse

Link to the code that reproduces this issue

https://github.com/Mrelijman/next16.2bug/tree/main/my-next-issue

To Reproduce

Clone https://github.com/Mrelijman/next16.2bug/tree/main/my-next-issue
Run npm install
Run npm run build

Build will fail with: TypeError: Cannot read properties of undefined (reading 'default') at Array.map at .next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053

Current vs. Expected behavior

Current: Turbopack build fails during static page prerendering with:

TypeError: Cannot read properties of undefined (reading 'default')
    at <unknown> (.next/server/chunks/ssr/[root-of-the-server]__09~zrn2._.js:6:1053)
    at Array.map (<anonymous>)
    at aW (...js:6:1031)
    at aX (...js:6:1248)
    at aY (...js:6:1613)

Expected: Build succeeds, as it did on Next.js 16.1.7 with identical code. The crash happens inside Next.js's own bundled SSR chunk, not in user code. The three ingredients required to reproduce:

app/icon.tsx that returns Response.redirect() as default export
import 'firebase-admin/app' anywhere in icon.tsx
next-intl plugin wrapping the Next.js config + a rewrite pointing favicon.ico → /icon

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows Server 2022 Standard
Binaries:
  Node: 24.11.1
  npm: 11.11.1
Relevant Packages:
  next: 16.2.0
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next build (local)

Additional context

next build --webpack succeeds on 16.2.0 — Turbopack specific
[email protected] with identical code builds fine — clean regression
On Windows there is no stack trace, just a digest, making this extremely hard to diagnose. The error points to /_not-found in the real project (not the actual icon.tsx file), sending debugging in completely the wrong direction
Took several hours to isolate because the error message is totally misleading
Tested [email protected] — still fails, suggesting not yet fixed

extent analysis

Fix Plan

To fix the Turbopack build failure, convert the app/icon.tsx file to a proper route handler.

Create a new file app/icon/route.ts with the following content:

import { NextResponse } from 'next/server';

export async function GET() {
  return NextResponse.redirect(new URL('/new-url', 'https://example.com'));
}

Remove the app/icon.tsx file or update it to not use Response.redirect() as the default export.
Update the next-intl plugin configuration to point to the new route handler if necessary.

Verification

After applying the fix, run npm run build to verify that the build succeeds.

Extra Tips

When using next-intl and Turbopack, ensure that all route handlers are properly defined and exported.
Be cautious when using Response.redirect() as the default export in route handlers, as it may cause issues with Turbopack.
If you encounter similar issues, try to isolate the problem by removing or updating individual components and configurations.

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nextjs - 💡(How to fix) Fix Turbopack 16.2.0 regression: app/icon.tsx returning Response.redirect() + firebase-admin import + next-intl crashes build with "Cannot read properties of undefined (reading 'default')" [2 comments, 2 participants]

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Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

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nextjs - 💡(How to fix) Fix Turbopack 16.2.0 regression: app/icon.tsx returning Response.redirect() + firebase-admin import + next-intl crashes build with "Cannot read properties of undefined (reading 'default')" [2 comments, 2 participants]

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Error Message

Root Cause

Fix Action

Fix / Workaround

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Fix Plan

Verification

Extra Tips

Still need to ship something?

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