How to make the scroll event not fire?

Question

JavaScript

Good afternoon. I have a header that adds the header--fixed class when scrolling.

const header = document.querySelector('.header');

window.addEventListener('scroll', () => {
  if (window.pageYOffset >= 1) {
    header.classList.add('header--fixed');
  } else {
    header.classList.remove('header--fixed');
  }
});

When opening a modal window, the scroll is removed and the scroll event fires. As a result, window.pageYOffset shows that it is at the very top of the page and the header--fixed class is removed.
How can I make the event not fire under such conditions? Or mb some kind of check can be done?