TypeError: App_1.apiUrl is not a function

I'm confused as to why a function I export from one React TypeScript module fails when imported into another module.

export const apiUrl = () : string => (process.env.NODE_ENV === 'development') ?
    "https://localhost:5001" : "https://my.azure.site.net";

I'm aware this is not the best way to set environment-specific info but it seemed like an expedient way to do this as a quick way to test the Azure service.

When I import apiUrl into other modules I get the TypeError.

import { apiUrl } from './App';
console.log(apiUrl());

TypeError: App_1.apiUrl is not a function. (In 'App_1.apiUrl()', 'App_1.apiUrl' is undefined)

And the function is undefined. So much for expedience. I've tried a couple of permutations, including exporting a const string:

export const apiUrl = (process.env.NODE_ENV === 'development') ? "https://localhost:5001" : "https://my.azure.site.net";

In all cases the imported object is undefined.

Update: I've established that if I use the string or method inside a class method then it works, i.e. when I call it in the componentDidMount method. What am I missing about scope here?