Hi, I'm trying the quoted code. function progressBarUpdate(tween) { console.log(tween.progress()) } const tl = gsap.timeline({ delay: 1, onUpdate: progressBarUpdate, }); tl .add(animate()) .add(reveal(), 'reveal') .add(start())   The timeline itself works perfectly. I just added onUpdate: progressBarUpdate and the function, and I get this error: The problem comes from this line console.log(tween.progress())   Any idea?