Scalafmt returns illegal start of simple expression on this

hardToFormat.scala

//scalafmt returns: error: illegal start of simple expression
  def validStringLength(min: Int, max: Int): String => Boolean = {
    s =>
      val len: Int = s.length
      (min <= len) && (len <= max)
  }

//scalafmt is fine with this
  def validStringLength(min: Int, max: Int): String => String => Boolean = 
    s => {
      val len: Int = s.length
      (min <= len) && (len <= max)
  }