How to send HttpStatus reasonPhrase/StatusDescription in addition to status code with ResponseEntity in Spring Rest

Question

I am using below ControllerAdvice to return error response. But vendor who are writing client code are complaining that they don't get reasonPhrase/StatusDescription with this. They are expecting 'Bad Request'. They using vb.net. Told them it will be easy to use enum System.Net.HttpStatusCode to get reasonPhrase/StatusDescription . But that will cost extra. How do I send reasonPhrase/StatusDescription with this response?

I think they getting something like and expecting StatusDescription should contain "Bad Request". We are deploying server code as jar and not using Tomcat.

    StatusCode        : 400
    StatusDescription :
    Content           : Constrained value error.


/**
 * @param constrainedValueNotFoundException - exception object
 * @return - ResponseEntity with http status code and error message
 */
@ExceptionHandler(value = ConstrainedValueNotFoundException.class)
public ResponseEntity<String> constrainedValueNotFoundException(
        ConstrainedValueNotFoundException constrainedValueNotFoundException) {
    logError(constrainedValueNotFoundException);
    return new ResponseEntity<>(
            constrainedValueNotFoundException.getLocalizedMessage(), BAD_REQUEST);
}