TS1259: Module can only be default-imported using esModuleInterop - in CI

By Daniel Zoghalchali·Latchkey

A CommonJS module with an export-assignment is default-imported, which TypeScript allows only with esModuleInterop.

What this error means

Type-checking fails with TS1259 telling you to enable esModuleInterop for a default import.

src/server.ts(1,8): error TS1259: Module '"express"' can only be default-imported using the 'esModuleInterop' flag.

Common causes

How to fix it

Enable esModuleInterop

1. Set esModuleInterop true (and allowSyntheticDefaultImports follows from it)

{
  "compilerOptions": { "esModuleInterop": true }
}

Use import-equals or namespace import

1. Without interop, use import express = require("express") or import * as express

import * as express from 'express'

How to prevent it

• Enable esModuleInterop project-wide so CommonJS default imports work consistently.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation