Disable HTML escaping when converting Protobuf to JSON

Given a simple Protobuf message

message MessageWithUrl {

  string url_params = 1;

}

I'm doing the following:

Msg.MessageWithUrl message = Msg.MessageWithUrl
                .newBuilder()
                .setUrlParams("?key=value")
                .build();

String json = JsonFormat.printer()
                .print(message);

System.out.println(json);

My expected outcome is:

{
  "urlParams": "?key=value"
}

Instead I get:

{
  "urlParams": "?key\u003dvalue"
}

I understand that the printer is using Gson under the hood, but I don't know how to have it accept the Gson option of disableHtmlEscaping