Web request with empty response (no content type)

I'm sending a web request with a command to a server. The response is empty and has no content type.

I tried omitting the responseType, but I still get a -400 error. I also tried explicitly specifying different response types (URL encoded, JSON, and plain text), but each attempt still returns a -400.

Is there a way to get the SDK to accept a response with an empty content type?

Of course, I could just ignore the -400 response code, but maybe there's a better solution?