HTTP/0.9 is the predecessor to HTTP/1.x. One big difference between HTTP/0.9 and HTTP/1.x is that HTTP/0.9 lacks any response headers. So when we send an HTTP/1.x request, if the server responds with a message that doesn't look like HTTP/1.x, we just assume it's an HTTP/0.9 response and treat the entire response is the response body, with no headers. We're removing this behavior except on default ports, and plan to further reduce support in the future.