diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameEventRenderer.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameEventRenderer.scala
index f74df264d9..5f3bf90604 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameEventRenderer.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameEventRenderer.scala
@@ -5,7 +5,7 @@
 package akka.http.impl.engine.ws
 
 import akka.util.ByteString
-import akka.stream.stage.{ TerminationDirective, StatefulStage, SyncDirective, Context }
+import akka.stream.stage.{ StatefulStage, SyncDirective, Context }
 
 import scala.annotation.tailrec
 
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameHandler.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameHandler.scala
index ed0128a07b..c405c234c1 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameHandler.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/FrameHandler.scala
@@ -5,7 +5,7 @@
 package akka.http.impl.engine.ws
 
 import akka.stream.scaladsl.Flow
-import akka.stream.stage.{ TerminationDirective, SyncDirective, Context, StatefulStage }
+import akka.stream.stage.{ SyncDirective, Context, StatefulStage }
 import akka.util.ByteString
 import Protocol.Opcode
 
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketLowLevel.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketLowLevel.scala
index 771171a9af..82716d58a0 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketLowLevel.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketLowLevel.scala
@@ -5,8 +5,7 @@
 package akka.http.impl.engine.ws
 
 import akka.http.scaladsl.model.HttpResponse
-import akka.http.scaladsl.model.ws.{ Message, UpgradeToWebsocket }
-import akka.stream.Materializer
+import akka.http.scaladsl.model.ws.UpgradeToWebsocket
 import akka.stream.scaladsl.Flow
 
 /**
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketsResponseHeader.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketsResponseHeader.scala
index 7b37733021..37970943b9 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketsResponseHeader.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/UpgradeToWebsocketsResponseHeader.scala
@@ -6,7 +6,6 @@ package akka.http.impl.engine.ws
 
 import akka.http.scaladsl.model.headers.CustomHeader
 import akka.http.scaladsl.model.ws.Message
-import akka.stream.Materializer
 import akka.stream.scaladsl.Flow
 
 private[http] final case class UpgradeToWebsocketResponseHeader(handler: Either[Flow[FrameEvent, FrameEvent, Any], Flow[Message, Message, Any]])
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Decoder.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Decoder.scala
index 2c7396c725..6cc6f655aa 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Decoder.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Decoder.scala
@@ -6,7 +6,6 @@ package akka.http.impl.engine.ws
 
 import akka.util.ByteString
 
-import scala.annotation.tailrec
 import scala.util.Try
 
 /**
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Encoder.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Encoder.scala
index 74d65d50ab..1b6c517bab 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Encoder.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Utf8Encoder.scala
@@ -7,8 +7,6 @@ package akka.http.impl.engine.ws
 import akka.stream.stage._
 import akka.util.{ ByteStringBuilder, ByteString }
 
-import scala.annotation.tailrec
-
 /**
  * A utf16 (= Java char) to utf8 encoder.
  *
diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Websocket.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Websocket.scala
index 136245b3f4..c3c4bce2fa 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Websocket.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/ws/Websocket.scala
@@ -6,13 +6,11 @@ package akka.http.impl.engine.ws
 
 import java.util.Random
 import akka.event.LoggingAdapter
-import akka.stream.impl.fusing.GraphInterpreter
 import akka.util.ByteString
 import scala.concurrent.duration._
 import akka.stream._
 import akka.stream.scaladsl._
 import akka.stream.stage._
-import akka.http.impl.util._
 import akka.http.scaladsl.model.ws._
 import akka.stream.impl.fusing.SubSource
 
@@ -37,9 +35,9 @@ private[http] object Websocket {
 
   /** The lowest layer that implements the binary protocol */
   def framing: BidiFlow[ByteString, FrameEvent, FrameEvent, ByteString, Unit] =
-    BidiFlow.fromFlowsMat(
+    BidiFlow.fromFlows(
       Flow[ByteString].via(FrameEventParser),
-      Flow[FrameEvent].transform(() ⇒ new FrameEventRenderer))(Keep.none)
+      Flow[FrameEvent].transform(() ⇒ new FrameEventRenderer))
       .named("ws-framing")
 
   /** The layer that handles masking using the rules defined in the specification */
@@ -54,9 +52,9 @@ private[http] object Websocket {
   def frameHandling(serverSide: Boolean = true,
                     closeTimeout: FiniteDuration,
                     log: LoggingAdapter): BidiFlow[FrameEventOrError, FrameHandler.Output, FrameOutHandler.Input, FrameStart, Unit] =
-    BidiFlow.fromFlowsMat(
+    BidiFlow.fromFlows(
       FrameHandler.create(server = serverSide),
-      FrameOutHandler.create(serverSide, closeTimeout, log))(Keep.none)
+      FrameOutHandler.create(serverSide, closeTimeout, log))
       .named("ws-frame-handling")
 
   /**
@@ -132,7 +130,6 @@ private[http] object Websocket {
       val merge = b.add(BypassMerge)
       val messagePreparation = b.add(prepareMessages)
       val messageRendering = b.add(renderMessages.via(LiftCompletions))
-      // val messageRendering = b.add(renderMessages.transform(() ⇒ new LiftCompletions))
 
       // user handler
       split.out1 ~> messagePreparation