Error when running next build in nextjs monorepo turborepo

I have a turborepo with 2 NextJS projects in it.

When I run next build I get this error:

[TypeError: Cannot read properties of null (reading 'useContext')]
Error occurred prerendering page "/404". Read more: https://nextjs.org/docs/messages/prerender-error
TypeError: Cannot read properties of null (reading 'useContext')
    at exports.useContext (/Users/user/dev/repos/repo-root/node_modules/styled-jsx/node_modules/react/cjs/react.production.js:488:33)

Package.json of app A

{
  "name": "docs",
  "version": "0.1.0",
  "type": "module",
  "private": true,
  "scripts": {
    "dev": "next dev --turbopack -p 3001",
    "build": "next build",
    "start": "next start",
    "lint": "next lint --max-warnings 0",
    "check-types": "tsc --noEmit"
  },
  "dependencies": {
    "next": "^15.2.1",
    "react": "^19.1.0",
    "react-dom": "^19.1.0"
  },
  "devDependencies": {
    "@types/node": "^22.13.10",
    "@types/react": "19.0.0",
    "@types/react-dom": "19.0.0",
    "eslint": "^9.22.0",
    "typescript": "5.8.2"
  }
}

Package.json of app B

{
  "name": "app",
  "version": "0.1.0",
  "type": "module",
  "private": true,
  "scripts": {
    "dev": "next dev --turbopack -p 3002",
    "build": "next build",
    "start": "next start",
    "lint": "next lint --max-warnings 0",
    "check-types": "tsc --noEmit"
  },
  "dependencies": {
    "next": "^15.2.1",
    "react": "19.0.0",
    "react-dom": "19.0.0"
  },
  "devDependencies": {
    "@types/node": "^22.13.10",
    "@types/react": "19.0.0",
    "@types/react-dom": "19.0.0",
    "eslint": "^9.22.0",
    "typescript": "5.8.2"
  }
}

I tried creating a custom 404 and/or error pages without any success.

You need to use the same react and react-dom version for your packages/apps in your monorepo. Also put ^ before the version number.

For this specific case change your apps' A and B package.json dependencies to this:

    "react": "^19.1.0",
    "react-dom": "^19.1.0"

Source: There's a comment in Vercel's next repo that explains it in more detail: link