ng-lazyload-image: Offset doesn't work

I wanted to improve appearance of the images via setting an offset to load the image beforehand. But it still does trigger the request when the image is already in the viewport.

Setting it like:

<img defaultImage="https://via.placeholder.com/400x800"
                 [offset]="300"
                 lazyLoad="../../assets/images/phones/phone@3x.png"/>