Console error

Warning: Failed prop type: Invalid prop className supplied to Modal. Warning: Failed prop type: Invalid prop overlayClassName

[danphilibin]

Leaving this solution here in case anyone has the same issue… in my case I had only included the base property in the className object. The error went away when I defined all three properties:

<Modal
  className={{
    base: 'modal', 
    afterOpen: 'modal-in',
    beforeClose: 'modal-out'
  }}
  overlayClassName={{
    base: 'modal-overlay', 
    afterOpen: 'modal-overlay-in',
    beforeClose: 'modal-overlay-out'
  }}
></Modal>

[fallenleavesguy]

I think it is cause by empty css class rules, empty css will be remove by css-loader or something other, so you get empty string when you import styles in css modules