CSS sibling selectors (select all siblings)

Usually, I'm good with CSS, but I can't seem to figure this one out. If I have a structure of

<div>
    <h2 class="open">1</h2>
    <h2>2</h2>
    <h2>3</h2>
    <h2>4</h2>
    <h2>5</h2>
</div>

how can I target all of the sibling h2s using the .open class with CSS? My main issue is that sibling selectors (.open + h2) will only target the h2 immediately following .open.