Can't compile in an es6 typescript project

[horrendo]

This is quite likely due to my inexperience with es6, but I'm in the process of migrating a typescript project from commonjs to es6, and I'm stuck.

I've created a small test case at https://github.com/horrendo/aws4-test. The README shows the error I'm getting. It also shows a workaround which I'd like to avoid if possible.

I'd appreciate any help.

Thanks !!