ts-r
  • Error
  • Reported by the binder

TS2664

Invalid module name in augmentation, module '{0}' cannot be found.

A declare module augmentation names a module that can't be resolved. Fix the module name or install the package being augmented.

What it means

A declare module "name" { ... } inside a module file augments an existing module, so the name has to resolve to one. Here it doesn't resolve to any file or package.

Example

index.ts
declare module "missing-lib" {
  export const extra: number;
}
export {};
ts-r-check -p tsconfig.json --pretty false ts-r output
index.ts(1,16): error TS2664: Invalid module name in augmentation, module 'missing-lib' cannot be found.

Recorded by node scripts/verify-examples.mjs with ts-r built from commit 6deaf01. The example uses the default tsconfig: strict, target: es2022, module: esnext, moduleResolution: bundler.

How to fix

  • Check the module name for typos; it must match what import would resolve.
  • Install the package (or its types) that you're augmenting.
  • If you meant to declare a module that has no types, put declare module "name" in a .d.ts file that is not itself a module (no top-level import/export).