prefixed(prop, prefix) {
    let spec
    ;[spec, prefix] = flexSpec(prefix)
    if (spec === 2009) {
      return prefix + 'box-align'
    }
    if (spec === 2012) {
      return prefix + 'flex-align'
    }
    return super.prefixed(prop, prefix)
  }
Change property name for 2009 and 2012 specs