AWS STS support?

[aptly-io]

I used httpie aws auth4 successfully with my access key & secret.
I tried to use it also with the access key & secret returned by AWS STS service. But then this fails.
Is it supposed to fail?

(I've a feeling one should also use the session token returned by the STS service).

It seems David Muller's implementation has support for the session token in one of the examples in the README.md

Thanks