diff --git a/akka-stream-tck/src/test/scala/akka/stream/tck/ActorPublisherTest.scala b/akka-stream-tck/src/test/scala/akka/stream/tck/ActorPublisherTest.scala
index b9b3737f21..50ec8eff52 100644
--- a/akka-stream-tck/src/test/scala/akka/stream/tck/ActorPublisherTest.scala
+++ b/akka-stream-tck/src/test/scala/akka/stream/tck/ActorPublisherTest.scala
@@ -38,7 +38,7 @@ object ActorPublisherTest {
 
 }
 
-class ActorPublisherTest extends AkkaPublisherVerification[Int](true) {
+class ActorPublisherTest extends AkkaPublisherVerification[Int] {
 
   override def createPublisher(elements: Long): Publisher[Int] = {
     val ref = system.actorOf(Props(classOf[TestPublisher], elements).withDispatcher("akka.test.stream-dispatcher"))
diff --git a/akka-stream-tck/src/test/scala/akka/stream/tck/HeadSinkSubscriberTest.scala b/akka-stream-tck/src/test/scala/akka/stream/tck/HeadSinkSubscriberTest.scala
new file mode 100644
index 0000000000..e01bb69247
--- /dev/null
+++ b/akka-stream-tck/src/test/scala/akka/stream/tck/HeadSinkSubscriberTest.scala
@@ -0,0 +1,19 @@
+/**
+ * Copyright (C) 2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+package akka.stream.tck
+
+import akka.stream.scaladsl._
+import org.reactivestreams.Subscriber
+
+import scala.concurrent.Promise
+
+class HeadSinkSubscriberTest extends AkkaSubscriberBlackboxVerification[Int] {
+  import HeadSink._
+
+  override def createSubscriber(): Subscriber[Int] =
+    new HeadSinkSubscriber[Int](Promise[Int]())
+
+  override def createHelperPublisher(elements: Long) =
+    createSimpleIntPublisher(elements)
+}
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl/ActorFlowSink.scala b/akka-stream/src/main/scala/akka/stream/scaladsl/ActorFlowSink.scala
index fdd33d4c62..2c36723d9f 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/ActorFlowSink.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/ActorFlowSink.scala
@@ -96,6 +96,19 @@ final case class FanoutPublisherSink[In](initialBufferSize: Int, maximumBufferSi
 
 object HeadSink {
   def apply[T](): HeadSink[T] = new HeadSink[T]
+
+  /** INTERNAL API */
+  private[akka] class HeadSinkSubscriber[In](p: Promise[In]) extends Subscriber[In] {
+    private val sub = new AtomicReference[Subscription]
+    override def onSubscribe(s: Subscription): Unit =
+      if (!sub.compareAndSet(null, s)) s.cancel()
+      else s.request(1)
+
+    override def onNext(t: In): Unit = { p.trySuccess(t); sub.get.cancel() }
+    override def onError(t: Throwable): Unit = p.tryFailure(t)
+    override def onComplete(): Unit = p.tryFailure(new NoSuchElementException("empty stream"))
+  }
+
 }
 
 /**
@@ -117,15 +130,7 @@ class HeadSink[In] extends KeyedActorFlowSink[In] {
   override def isActive = true
   override def create(materializer: ActorBasedFlowMaterializer, flowName: String) = {
     val p = Promise[In]()
-    val sub = new Subscriber[In] { // TODO #15804 verify this using the RS TCK
-      private val sub = new AtomicReference[Subscription]
-      override def onSubscribe(s: Subscription): Unit =
-        if (!sub.compareAndSet(null, s)) s.cancel()
-        else s.request(1)
-      override def onNext(t: In): Unit = { p.trySuccess(t); sub.get.cancel() }
-      override def onError(t: Throwable): Unit = p.tryFailure(t)
-      override def onComplete(): Unit = p.tryFailure(new NoSuchElementException("empty stream"))
-    }
+    val sub = new HeadSink.HeadSinkSubscriber[In](p)
     (sub, p.future)
   }