HTTP error 404 from spring web causes "404 null" message in RestTemplate

I noticed that in RestTemplate-based client, I'm getting error messages like 404 null and similar. Then I found that the Spring Boot application returns error statuses like the following:

> curl -v http://localhost:8080/page-not-found
(...)
< HTTP/1.1 404
< Content-Type: application/json;charset=UTF-8

which will look like this:

org.springframework.web.client.HttpClientErrorException$NotFound: 404 null

Others return results like:

curl -v http://google.com/page-not-found
(...)
< HTTP/1.1 404 Not Found
< Content-Type: text/html; charset=UTF-8

Which results in a nice looking error message:

org.springframework.web.client.HttpClientErrorException$NotFound: 404 Not Found

I'm not sure if I should raise is as a bug - it does not seem that the status message is mandatory.

Is this a bug, or a feature?