jQueryValidate - Required field - depends doesn't work

With jQueryValidate, I'm trying to make a field required only if another specific field is empty. So, after searching on the Internet, I did this :

rules: {
     marque: {
          required: {
               depends: function() {
                    if (($('#add_marque').val() == "Ajouter une marque" && $('#marque').val() == -1) || ($('#add_marque').val() == "" && $('#marque').val() == -1)) {
                         return true;
                     }
                     else {
                         return false;
                     }
               }
          }
     }
}

Unfortunately, it doesn't work. But, if I do this :

depends: function() {
     if (($('#add_marque').val() == "Ajouter une marque" && $('#marque').val() == -1) || ($('#add_marque').val() == "" && $('#marque').val() == -1)) {
          alert("Here!");
          return true;
      }
      else {
           return false;
      }
}

The alert box appears. So, my test seems to work. Can anyone tell me what I did wrong? I'm using jQuery 1.8.3 and qTip2 with jQueryValidate. Thank you very much!