Strange inset shadow in FF 45.0a1 (2015-11-22)

HTML

<div class="test first"></div>
<div class="test second"></div>
<div class="test third"></div>

CSS

.test {
    background-color: #fec;
    display: inline-block;
    width: 5em;
    height: 5em;
}
.first {
    box-shadow: inset 0 0 1px -3px rgba(0,0,10,0.25);
}
.second {
    box-shadow: inset 0 5px 1px -20px rgba(0,0,10,0.25);
}
.third {
    box-shadow: 0 5px 1px -3px rgba(0,0,10,0.25);
}