Adding a class doesn't override backgroundColor

If I do NOT set a backgroundColor option when calling Toastify, but add a className that maps for instance to a Bootstrap alert class, the Toast’s default backgroundColor still takes precedence over the class’ background color.

i.e.

 Toastify({
    text: "A simple warning alert—check it out!",
    duration: 3000,
    close: true,
    gravity: "bottom",
    positionLeft: false,
    className:"alert alert-warning>"
    }).showToast();

Should yield the following:

Instead I get:

[CharlieIGG]

FYI I ended up doing the following to achieve what I wanted (thankfully I was already packing SCSS):

@each $color,
$value in $theme-colors {

  .toastify.alert-#{$color},
  .alert-#{$color} {
    @include alert-variant(theme-color-level($color, $alert-bg-level), theme-color-level($color, $alert-border-level), color-yiq(theme-color-level($color, $alert-bg-level)));

    .close,
    .alert-link {
      color: color-yiq(theme-color-level($color, $alert-bg-level));
    }
  }
}

[patrickliu-hk]

I added one-line CSS to solve that

.toastify {
  background-image: unset;
}