Try css props and see if those work with the css function

Look into css props and try passing a css mixin.

import React from 'react'
import { css } from 'styled-components'

const cssMixin = css`
  color: blue;
`

const TestComponent = ({ children }) => <div css={cssMixin}>{children}</div>

// add prop types yada yada

export default TestComponent

Report to @apittori if this works. This would solve a plethora of styling problems with icons and <Icon>.