To reproduce:

1. npm install
2. npm run dev
3. Open pages/index.js
4. Add bg-red-100 to the className prop
5. Save the file
6. Add bg-red-200 to the className prop
7. Save the file
8. Add bg-red-300 to the className prop
9. Save the file
10. Inspect the h1 element and see that the bg-red-100 and bg-red-200 classes are duplicated