diff --git a/akka-docs-dev/rst/scala/code/docs/stream/io/StreamFileDocSpec.scala b/akka-docs-dev/rst/scala/code/docs/stream/io/StreamFileDocSpec.scala
index d297c3cba3..e212df54be 100644
--- a/akka-docs-dev/rst/scala/code/docs/stream/io/StreamFileDocSpec.scala
+++ b/akka-docs-dev/rst/scala/code/docs/stream/io/StreamFileDocSpec.scala
@@ -14,6 +14,8 @@ import akka.stream.testkit.Utils._
 import akka.stream.testkit._
 import akka.util.ByteString
 
+import scala.concurrent.Future
+
 class StreamFileDocSpec extends AkkaSpec(UnboundedMailboxConfig) {
 
   implicit val ec = system.dispatcher
@@ -45,8 +47,9 @@ class StreamFileDocSpec extends AkkaSpec(UnboundedMailboxConfig) {
 
     //#file-source
 
-    SynchronousFileSource(file)
-      .runForeach((chunk: ByteString) ⇒ handle(chunk))
+    val foreach: Future[Long] = SynchronousFileSource(file)
+      .to(Sink.ignore)
+      .run()
     //#file-source
   }
 
diff --git a/akka-stream/src/main/scala/akka/stream/io/InputStreamSource.scala b/akka-stream/src/main/scala/akka/stream/io/InputStreamSource.scala
index 3c81fa40b0..16bb322843 100644
--- a/akka-stream/src/main/scala/akka/stream/io/InputStreamSource.scala
+++ b/akka-stream/src/main/scala/akka/stream/io/InputStreamSource.scala
@@ -36,7 +36,7 @@ object InputStreamSource {
    *
    * It materializes a [[Future]] containing the number of bytes read from the source file upon completion.
    */
-  def create(createInputStream: Creator[InputStream]): javadsl.Source[ByteString, Future[Long]] =
+  def create(createInputStream: Creator[InputStream]): javadsl.Source[ByteString, Future[java.lang.Long]] =
     create(createInputStream, DefaultChunkSize)
 
   /**
@@ -47,7 +47,7 @@ object InputStreamSource {
    *
    * It materializes a [[Future]] containing the number of bytes read from the source file upon completion.
    */
-  def create(createInputStream: Creator[InputStream], chunkSize: Int): javadsl.Source[ByteString, Future[Long]] =
-    apply(() ⇒ createInputStream.create(), chunkSize).asJava
+  def create(createInputStream: Creator[InputStream], chunkSize: Int): javadsl.Source[ByteString, Future[java.lang.Long]] =
+    apply(() ⇒ createInputStream.create(), chunkSize).asJava.asInstanceOf[javadsl.Source[ByteString, Future[java.lang.Long]]]
 
 }
diff --git a/akka-stream/src/main/scala/akka/stream/io/OutputStreamSink.scala b/akka-stream/src/main/scala/akka/stream/io/OutputStreamSink.scala
index 436bf5dbde..91fa91b3ed 100644
--- a/akka-stream/src/main/scala/akka/stream/io/OutputStreamSink.scala
+++ b/akka-stream/src/main/scala/akka/stream/io/OutputStreamSink.scala
@@ -38,7 +38,7 @@ object OutputStreamSink {
    *
    * Materializes a [[Future]] that will be completed with the size of the file (in bytes) at the streams completion.
    */
-  def create(f: Creator[OutputStream]): javadsl.Sink[ByteString, Future[Long]] =
-    apply(() ⇒ f.create()).asJava
+  def create(f: Creator[OutputStream]): javadsl.Sink[ByteString, Future[java.lang.Long]] =
+    apply(() ⇒ f.create()).asJava.asInstanceOf[javadsl.Sink[ByteString, Future[java.lang.Long]]]
 
 }
diff --git a/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSink.scala b/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSink.scala
index de7175b9dd..10da78cdce 100644
--- a/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSink.scala
+++ b/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSink.scala
@@ -28,7 +28,7 @@ object SynchronousFileSink {
    * unless configured otherwise by using [[ActorOperationAttributes]].
    */
   def apply(f: File, append: Boolean = false): Sink[ByteString, Future[Long]] =
-    new Sink(new SynchronousFileSink(f, append, DefaultAttributes, Sink.shape("SynchronousFileSink")))
+    new Sink(new impl.SynchronousFileSink(f, append, DefaultAttributes, Sink.shape("SynchronousFileSink")))
 
   /**
    * Java API
@@ -41,8 +41,8 @@ object SynchronousFileSink {
    * This source is backed by an Actor which will use the dedicated `akka.stream.file-io-dispatcher`,
    * unless configured otherwise by using [[ActorOperationAttributes]].
    */
-  def create(f: File): javadsl.Sink[ByteString, Future[Long]] =
-    apply(f, append = false).asJava
+  def create(f: File): javadsl.Sink[ByteString, Future[java.lang.Long]] =
+    apply(f, append = false).asJava.asInstanceOf[javadsl.Sink[ByteString, Future[java.lang.Long]]]
 
   /**
    * Java API
@@ -54,7 +54,7 @@ object SynchronousFileSink {
    * This source is backed by an Actor which will use the dedicated `akka.stream.file-io-dispatcher`,
    * unless configured otherwise by using [[ActorOperationAttributes]].
    */
-  def appendTo(f: File): javadsl.Sink[ByteString, Future[Long]] =
-    apply(f, append = true).asJava
+  def appendTo(f: File): javadsl.Sink[ByteString, Future[java.lang.Long]] =
+    apply(f, append = true).asInstanceOf[javadsl.Sink[ByteString, Future[java.lang.Long]]]
 
 }
diff --git a/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSource.scala b/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSource.scala
index a48131b155..3764c558ed 100644
--- a/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSource.scala
+++ b/akka-stream/src/main/scala/akka/stream/io/SynchronousFileSource.scala
@@ -41,7 +41,7 @@ object SynchronousFileSource {
    *
    * It materializes a [[Future]] containing the number of bytes read from the source file upon completion.
    */
-  def create(f: File): javadsl.Source[ByteString, Future[Long]] =
+  def create(f: File): javadsl.Source[ByteString, Future[java.lang.Long]] =
     create(f, DefaultChunkSize)
 
   /**
@@ -54,7 +54,7 @@ object SynchronousFileSource {
    *
    * It materializes a [[Future]] containing the number of bytes read from the source file upon completion.
    */
-  def create(f: File, chunkSize: Int): javadsl.Source[ByteString, Future[Long]] =
-    apply(f, chunkSize).asJava
+  def create(f: File, chunkSize: Int): javadsl.Source[ByteString, Future[java.lang.Long]] =
+    apply(f, chunkSize).asJava.asInstanceOf[javadsl.Source[ByteString, Future[java.lang.Long]]]
 
 }