Fix TypeScriptError: Type error: Property 'email' does not exist on type 'User'. in Next.js

This error occurs when TypeScript's strict type checking finds a property access that does not exist on the declared type. Next.js runs type checking during builds by default. Fix it by updating the type definition to include the missing property, or by correcting the property name to match the existing type.

Reading the Stack Trace

Here's what each line means:

• at createTypeError (/app/node_modules/next/dist/compiled/typescript/lib/typescript.js:154892:17): The TypeScript compiler creates the type error because the property access violates the declared type contract.
• at checkPropertyAccessExpressionOrQualifiedName (/app/node_modules/next/dist/compiled/typescript/lib/typescript.js:176234:32): TypeScript's property access checker verifies that 'email' exists on type 'User' and finds it missing.
• at checkExpression (/app/node_modules/next/dist/compiled/typescript/lib/typescript.js:181265:28): The expression {user.email} in the JSX template is being type-checked during the build phase.

Common Causes

interface User {
  id: number;
  name: string;
}

export default function ProfileCard({ user }: { user: User }) {
  return <p>{user.email}</p>; // 'email' not in User
}

interface User {
  id: number;
  name: string;
  emailAddress: string;
}

export default function ProfileCard({ user }: { user: User }) {
  return <p>{user.email}</p>; // Should be user.emailAddress
}

// types.ts - defined months ago
interface User {
  id: number;
  name: string;
}

// API now returns { id, name, email, avatar }
// Type was never updated

The Fix

Add the missing email property to the User interface so TypeScript recognizes it as a valid property access. This aligns the type definition with how the data is actually used in the component.

interface User {
  id: number;
  name: string;
}

export default function ProfileCard({ user }: { user: User }) {
  return (
    <div>
      <p>{user.email}</p>
      <p>{user.name}</p>
    </div>
  );
}

interface User {
  id: number;
  name: string;
  email: string;
}

export default function ProfileCard({ user }: { user: User }) {
  return (
    <div>
      <p>{user.email}</p>
      <p>{user.name}</p>
    </div>
  );
}

Testing the Fix

import { render, screen } from '@testing-library/react';
import ProfileCard from '@/components/ProfileCard';

describe('ProfileCard', () => {
  const user = { id: 1, name: 'Alice', email: 'alice@example.com' };

  it('renders the user email', () => {
    render(<ProfileCard user={user} />);
    expect(screen.getByText('alice@example.com')).toBeInTheDocument();
  });

  it('renders the user name', () => {
    render(<ProfileCard user={user} />);
    expect(screen.getByText('Alice')).toBeInTheDocument();
  });

  it('type-checks the User interface', () => {
    const invalidUser = { id: 1, name: 'Bob' };
    // @ts-expect-error - email is required
    expect(() => render(<ProfileCard user={invalidUser} />)).toBeDefined();
  });
});

Run your tests:

npm test

Pushing Through CI/CD

git checkout -b fix/typescript-user-type-email,git add src/types/user.ts src/components/ProfileCard.tsx src/components/__tests__/ProfileCard.test.tsx,git commit -m "fix: add email property to User type interface",git push origin fix/typescript-user-type-email

Your CI config should look something like this:

name: CI
on:
  pull_request:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npx tsc --noEmit
      - run: npm test -- --coverage
      - run: npm run build

The Full Manual Process: 18 Steps

Here's every step you just went through to fix this one bug:

1. Notice the error alert or see it in your monitoring tool
2. Open the error dashboard and read the stack trace
3. Identify the file and line number from the stack trace
4. Open your IDE and navigate to the file
5. Read the surrounding code to understand context
6. Reproduce the error locally
7. Identify the root cause
8. Write the fix
9. Run the test suite locally
10. Fix any failing tests
11. Write new tests covering the edge case
12. Run the full test suite again
13. Create a new git branch
14. Commit and push your changes
15. Open a pull request
16. Wait for code review
17. Merge and deploy to production
18. Monitor production to confirm the error is resolved

Total time: 30-60 minutes. For one bug.

npm install bugstack-sdk

import { initBugStack } from 'bugstack-sdk'

initBugStack({ apiKey: process.env.BUGSTACK_API_KEY })

Deploying the Fix (Manual Path)

1. Update the User type definition to include the missing property.
2. Run tsc --noEmit locally to verify no type errors remain.
3. Open a pull request with the type and component changes.
4. Wait for CI checks to pass on the PR.
5. Merge to main and verify the build succeeds in staging.

Frequently Asked Questions