Intersection observer not working in Safari

Question

I am creating a simple navbar, which toggles background (via class ".nav-bg"), when it reaches end of first page (".hero"). It works 10/10 on Firefox/Chrome but doesn't work on Edge and Safari. I can't figure out why.

Code:

const observer = new IntersectionObserver(entries =>{
    document.querySelector(".navbar").classList.toggle("nav-bg", entries[0].intersectionRatio < 0.1);
  }, {
    threshold: 0.1
   });
  
    observer.observe(document.querySelector(".hero"));