Unfortunately, the .d.ts file is generated automatically through tsd-jsdoc and as thus needs a fix on jsdoc level.

Edit: Could you let me know of your specific use case? For me, this seems to work:

(protobuf.load("hello.proto") as Promise<protobuf.Root>).then((root) => {
    ...
});

Should work without type hints now (I believe nobody would use the non-promise return value anyway).

Hey, sorry for the late reply. Thanks for fixing this!

Using typescript 1.8 it complains about "Object" not having a then property. And I wouldn't like to make the as Promise... correction, too verbose :)

The fix isn't published on npm, yet, so you are probably still using a .d.ts with the Promise<Root> | Object return signature. The fix above changed the return signature to Promise<Root> | undefined which properly infers to Promise<Root> when appending .then(...).