User-Agent in Webhooks Calls

It’s possible that if I define User-Agent inside a Webhook event in the header_map inside the handler_meta, Tyk ignores my definition and redefine it as ‘Tyk-Hookshot’ ?
I’m using a lowercase user-agent definition and see in the code that Tyk add a ‘User-Agent’ header.
I try to put as ‘User-Agent’ also to see if I can overwrite Tyk definition…

Tyk will override it as Tyk-Hookshot because (I think) it gets set after the request is built.