Fire event with this.emit(...)?

Hm.. For whatever reason, it works now.. I'm a bit embarrassed.. Just for reference, code is here:

function aClass() {};
aClass.prototype.testEmit = function() {
  setTimeout(()=>this.emit('TestEvent'), 1000); 
}
var a = new aClass();
a.on('TestEvent', ()=>console.log('Got event')); 
a.testEmit();  // get 'Got event' printed in log
var a1 = new aClass();
a1.testEmit(); // event here is not caught