How do I avoid (globalThis as any) when using TS?

There has to be a magic trick or declaration you can put somewhere.

I'd like to do a globalThis.blah = () => {}; but I am forced to do (globalThis as any).blah = () => {};.

I do have a main.ts file and I have a:

declare global {

}

at the top. Any ideas? var globalthis: any; ??

It looks like this does the trick:

declare global {
 var foo: number;
}

// no longer an error
globalThis.foo = 1;