How to add mutiple class in emotion-js

Question

In react, using emotion.js

<div css={css`
    width: 30px;
    height: 20px;
`}></div>

This code generate in dom will be like this

<div class="css-1uy6h0w"></div>

I want to add some new class to this element, when some event happened

It added new class, not replace class.

<div class="css-1uy6h0w css-uyn2zx css-1hdvlqc"></div> // two classname