'File name differs from already included file name only in casing' on relative path with same casing

Error TS1149: File name 'C:/Project/frontend/scripts/State.ts' differs from already included file name '../frontend/scripts/State.ts' only in casing.

I've triple checked the casing in our references and the actual files have the correct casing as well. As far as I can tell, this is solely because the relative path uses incorrect casing, or perhaps it's just because of the relative path itself?

The thing is, it compiles just fine on Mac and Linux, but throws this error on Windows.

If it helps, forceConsistentCasingInFileNames is enabled in the tsconfig, and we're using tsify to compile.

In my case, the error was in the import statement. The import statement had a capital letter instead of small letter, which worked during develop in Windows, but not when compiling for production.


import {SomeClass} from '/some/path/SomeClass.ts';


import {SomeClass} from '/some/path/someClass.ts';

You need to disable the "forceConsistentCasingInFileNames" in the tsconfig.json file.

So you should have something like that:

  "compilerOptions": {
    "forceConsistentCasingInFileNames": false,

The answer was that we were using tisfy 1.0.1, when forceConsistentCasingInFileNames wasn't supported until 4.0.0. Updating fixed the issue.

Changing "React" to "react" worked for me.


import React from "React";


import React from "react";

When two files exist in same folder with names like a.tsx and A.tsx you will get this error

  • what is tisfy ?
  • Updating what? please provide more info on what you updated