No content in 204 response in /bg endpoint

After a file is registered to the background knowledge, I can receive the 204 response on the next request, but there is no conetent as described in the README:

HTTP/1.1 204 No Content

Date: Mon, 16 Nov 2020 19:31:39 GMT

Content-Type: text/plain; charset=UTF-8

Connection: Keep-Alive

Content-Length: 107