[css] Combine :after with :hover

I want to combine :after with :hover in CSS (or any other pseudo selector). I basically have a list and the item with the selected class has an arrow shape applied using :after. I want the same to be true for objects that are being hovered over but cant quite get it to work. Heres the code

#alertlist
{
    list-style:none;
    width: 250px;
}
#alertlist li
{
    padding: 5px 10px;
    border-bottom: 1px solid #e9e9e9;
    position:relative;
}
#alertlist li.selected, #alertlist li:hover
{
    color: #f0f0f0;
    background-color: #303030;
}

#alertlist li.selected:after
{
    position:absolute;
    top: 0;
    right:-10px;
    bottom:0;

    border-top: 10px solid transparent;
    border-bottom: 10px solid transparent;
    border-left: 10px solid #303030;
    content: "";
}

<ul id="alertlist">
    <li>Alert 123</li>
    <li class="selected">Alert 123</li>
    <li>Alert 123</li>
</ul>

in scss

&::after{
content: url(images/RelativeProjectsArr.png);
margin-left:30px;
}

&:hover{
    background-color:$turkiz;
    color:#e5e7ef;

    &::after{
    content: url(images/RelativeProjectsArrHover.png);
    }
}

 #alertlist li:hover:after,#alertlist li.selected:after
{
    position:absolute;
    top: 0;
    right:-10px;
    bottom:0;

    border-top: 10px solid transparent;
    border-bottom: 10px solid transparent;
    border-left: 10px solid #303030;
    content: "";
}?

jsFiddle Link