Question: Why is rollup-plugin-purgecss outputting js?

[ghost]

Why does rollup-plugin-purgecss write js to the purged css files?
The purged css is wrapped in export default "...".

Expected result

/* main.css */

.div{background-color:black} ....

Actual behaviour

/* main.css */

export default ".div{background-color:black}...."