Spring ResponseStatusException does not return reason

I have a very simple @RestController, and I'm trying to set a custom error message. But for some reason, the message for the error is not showing up.

This is my controller:

@RestController@RequestMapping("openPharmacy")public class OpenPharmacyController {    @PostMapping    public String findNumberOfSurgeries(@RequestBody String skuLockRequest) {        throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "This postcode is not valid");    }}

This is the response that I get:

{"timestamp": "2020-06-24T17:44:20.194+00:00","status": 400,"error": "Bad Request","message": "","path": "/openPharmacy/"}

I'm passing a JSON, but I'm not validating anything, I'm just trying to set the custom message. If I change the status code, I see that on the response, but the message is always empty.

Why is this not working like expected? This is such a simple example that I can't see what may be missing. When I debug the code I can see that the error message has all the fields set. But for some reason, the message is never set on the response.