Missing grammar in JBoss Resteasy generated WADL

I managed to get a WADL by using the org.jboss.resteasy.wadl.ResteasyWadlServlet (http://stackoverflow.com/a/41471710/2528609), but the WADL does not contain the Grammar. The representation nodes also do not contain an element attribute defining the response type.

Given the following rest endpoint class

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

@Path("user")
public class UserEndpoint {

    @GET
    @Path("")
    @Produces(MediaType.APPLICATION_JSON)
    public UserResponse getUser() {
       UserResponse response = new UserResponse();
       response.name = "Michiel";
       response.age = 43;
       return response;
    }   
}

And

public class UserResponse {
    public String name;
    public int age;
}

I do get the correct JSON when navigating to the endpoint, but when navigating to the application.xml URL I get

The WADL does not describe the UserResponse class, nor does it indicate it as the element type of the getUser method.

I would have expected something like:

               ...
            

How do I get the generated WADL to include the grammar part?

This is my web.xml:

Archetype Created Web ApplicationRESTEasy WADLorg.jboss.resteasy.wadl.ResteasyWadlServletRESTEasy WADL/application.xml

These are the dependencies in my pom.xml:

org.jboss.resteasyresteasy-wadl3.0.19.Finalorg.jboss.resteasyresteasy-jaxrs

I use JBoss Wildfly 10.1.0.