Do not set the UTF charset in a RESTful POST

Hello. I'm working on a new connected system and integration. In the integration I need to post JSON data to an endpoint.

None of that is a problem except that I get a HTTP/1.1 415 Unsupported Media Type response from the connected system.

I'm able to connect to remote system using Postman without error. It looks to me that Appian is automatically inserting the UTF-8 charset in the content-type header: Content-Type: application/json; charset=UTF-8.

The addition of that charset causes the error from the remote system, which I can confirm in Postman.

Is there a way to exclude the charset when sending a POST?

Thanks.