Implicit resolution failing on 2.10.0-RC5 with type alias.

gistfile1.txt

Welcome to Scala version 2.10.0-RC5 (OpenJDK 64-Bit Server VM, Java 1.7.0_02).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import org.scalacheck._
import org.scalacheck._

scala> type ListString = List[String]
defined type alias ListString

scala> implicitly[Arbitrary[List[String] => List[String]]]
res0: org.scalacheck.Arbitrary[List[String] => List[String]] = org.scalacheck.Arbitrary$$anon$2@7e4cd909

scala> implicitly[Arbitrary[ListString => ListString]]
<console>:24: error: could not find implicit value for parameter e: org.scalacheck.Arbitrary[ListString => ListString]
              implicitly[Arbitrary[ListString => ListString]]
                        ^