Match multiple cases classes in scala

I'm doing matching against some case classes and would like to handle two of the cases in the same way. Something like this:

abstract class Foo
case class A extends Foo
case class B(s:String) extends Foo
case class C(s:String) extends Foo


def matcher(l: Foo): String = {
  l match {
    case A() => "A"
    case B(sb) | C(sc) => "B"
    case _ => "default"
  }
}

But when I do this I get the error:

(fragment of test.scala):10: error: illegal variable in pattern alternative
    case B(sb) | C(sc) => "B"

I can get it working of I remove the parameters from the definition of B and C but how can I match with the params?