Rapture: XML extraction problem

raptureXmlTest.scala

object RaptureXmlOk {
  import rapture.xml._

  case class Foo(bar: Bar)
  case class Bar(baz: Baz)
  case class Baz(qux: Qux)
  case class Qux(value: String)

  implicitly[Extractor[Bar, Xml]] // works
  implicitly[Extractor[Foo, Xml]] // works
}

// REPL
// :paste
// Entering paste mode (ctrl-D to finish)
// CTRL +D
// Exiting paste mode, now interpreting.
// defined object RaptureXmlOk

object RaptureXmlKo {
  import rapture.xml._, xmlBackends.stdlib._

  case class Foo(bar: Bar)
  case class Bar(baz: Baz)
  case class Baz(qux: Qux)
  object Baz {
    // custom extractor in order to be able to extract this:
    // xml"""<foo><bar><baz><value>xxx</value></baz></bar></foo>""".as[Foo]
    // i.e. without the extra <qux>...</qux>
    implicit val bazExtractor: Extractor[Baz, Xml] =
      Xml.extractor[Qux].map(Baz(_))
  }
  case class Qux(value: String)

  implicitly[Extractor[Bar, Xml]] // works
  implicitly[Extractor[Foo, Xml]] // fails!!!
}

// REPL
// :paste
// Entering paste mode (ctrl-D to finish)
// CTRL +D
// Exiting paste mode, now interpreting.
// <console>:27: error: cannot extract type RaptureXmlKo.Foo from rapture.xml.Xml.
//  implicitly[Extractor[Foo, Xml]] // fails!!!