Place checkbox embedded in the upper right of an image?

How do I place a checkbox embedded in the upper right of an image? This currently does not work

HTML:

<div class="container">
    <img src="https://images.unsplash.com/reserve/bOvf94dPRxWu0u3QsPjF_tree.jpg?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" />
    <input type="checkbox" class="checkbox" id="check1" />
</div>

CSS:

.container {
    position: relative;
    width: 100px;
    height: 100px;
    float: left;
    margin-left: 10px;
}

.checkbox {
    position: absolute;
    right: 5px;
    top: 5px;
}