Button.onClick does not work when I renamed

Hello, I have a little Script, when I renowned "Ok" to "Aceptar" and does not work, I pressed click, Enter, Spacebar, and Does not work

I have Adobe Illustrator CC2015

var button = new Window('dialog', ''); 

btnName = button.add('button',undefined,'Ok');  //btnName = button.add('button',undefined,'Aceptar');  //
btnName.onClick = function() {
alert ("Works!")    }
button.show();

    Run Script:

when I click in "aceptar", Alert does not show and "aceptar" button shows an orange edge

Help me Pls , Sorry my bad english