akka stream v2.0.1 TestSink.expectNextUnordered fails with java.lang.AssertionError: `remaining` may not be called outside of `within` but expectNext runs without any problems

gistfile1.txt

// dependencies
scalaVersion := "2.11.7"

libraryDependencies ++= {
  val akkaVersion = "2.4.1"
  val akkaStreamAndHttpVersion = "2.0.1"
  Seq(
    "com.typesafe.akka" %% "akka-actor" % akkaVersion,
    "com.typesafe.akka" %% "akka-slf4j" % akkaVersion,
    "com.typesafe.akka" %% "akka-persistence" % akkaVersion,
    "com.typesafe.akka" %% "akka-persistence-query-experimental" % akkaVersion,
    "com.typesafe.akka" %% "akka-stream-experimental" % akkaStreamAndHttpVersion,
    "com.typesafe.akka" %% "akka-stream-testkit-experimental" % akkaStreamAndHttpVersion % Test,
    "com.typesafe.akka" %% "akka-testkit" % akkaVersion % Test,
    "com.typesafe.akka" %% "akka-persistence-tck" % akkaVersion % Test,
    "org.scalatest" %% "scalatest" % "2.2.4" % Test
  )
}

// the test
import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.Source
import akka.stream.testkit.scaladsl.TestSink
import org.scalatest.{FlatSpec, Matchers}

class TestSinkTest extends FlatSpec with Matchers {
  implicit val system = ActorSystem()
  implicit val mat = ActorMaterializer()
  implicit val ec = system.dispatcher

  "expectNext" should "run with no problems" in {
    Source(List("my-1", "my-2"))
      .runWith(TestSink.probe[AnyRef])
      .request(3)
      .expectNext("my-1", "my-2")
      .expectComplete()
  }

  "expectNextUnordered" should "fail with java.lang.AssertionError: `remaining` may not be called outside of `within`" in {
    intercept[AssertionError] {
      Source(List("my-1", "my-2"))
        .runWith(TestSink.probe[AnyRef])
        .request(3)
        .expectNextUnordered("my-1", "my-2")
        .expectComplete()
    }
  }
}