Invalid css selector generated

[kdy1]

What version of Tailwind CSS are you using?

v3.4.14

What build tool (or framework if it abstracts the build tool) are you using?

Next.js + turbopack, but reproducible on playground.

What version of Node.js are you using?

Playground

What browser are you using?

Chrome

What operating system are you using?

macOS

Reproduction URL

https://play.tailwindcss.com/obgZakKyiO?file=css

Describe your issue

Generated CSS file is

p.my-4 {
  margin: 0px;
}
.\[\&_\:is\(p\)\]\:my-4 :is(p)p {
  margin: 0px;
}

where :is(p)p is invalid