Can not customize Content-Length Header in PUT Request

[yibizzi]

I'm trying to upload a file to AWS S3 using soapui. The raw request i'm building is :

However, when the request is sent, I don't see my pre-calculated content-length in the logs:

I can get to see it in the logs only when I set media-type to multipart/mixed, but it calculates another value for the header, and doesn't take my input into consideration.