Own button icon missing on platform windows

I’ve inserted some buttons with own icons in my app, using the following code (in app.scss):

ion-icon {
    &[class*="my-own-"] {
        mask-size: contain;
        mask-position: 50% 50%;
        mask-repeat: no-repeat;
        background: currentColor;
        width: 1em;
        height: 1em;
}
&[class*="my-own-icon"] {
    mask-image: url(../assets/img/my-on-icon.svg);
}

And on the particular page (in page.html):

  <button ion-button>
     <ion-icon name="my-on-icon"></ion-icon>
  </button>

It’s working fine on Android and iOS, but on Windows the icon inside the button is missing. What could be the problem?