Swiper.js bulletClass pagination doesn't work in Angular

I want to apply custom css to the pagination on my slider, but can't make it work, the pagination is gone when i specify bulletClass in Pagination.

in ts: Config object:

  config: SwiperConfigInterface = {
    spaceBetween: 30,
    centeredSlides: true,
    loop: true,
    effect: 'fade',
    pagination: {
      el: '.swiper-pagination',
      clickable: true,
       bulletClass: 'my-custom-pagination-bullet', // this doesn't work
    },
    autoplay: {
      delay: 4000,
      disableOnInteraction: false,
    },
    navigation: {
      nextEl: '.swiper-button-next',
      prevEl: '.swiper-button-prev'
    }
  };