diff --git a/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
index 32e8da50e7..1c589ed0d1 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
@@ -84,7 +84,7 @@ class MaterializationBenchmark {
   var graphWithNestedImports: RunnableGraph[NotUsed] = _
   var graphWithImportedFlow: RunnableGraph[NotUsed] = _
 
-  @Param(Array("1", "10", "100", "1000"))
+  @Param(Array("1", "10"))
   var complexity = 0
 
   @Setup
diff --git a/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala b/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
index d9aec3c41f..6dd7366fe3 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
@@ -47,8 +47,8 @@ private[akka] class ActorProcessor[I, O](impl: ActorRef) extends ActorPublisher[
  * INTERNAL API
  */
 private[akka] abstract class BatchingInputBuffer(val size: Int, val pump: Pump) extends DefaultInputTransferStates {
-  if (size < 1) throw new IllegalArgumentException(s"buffer size MSUT be positive (was: $size")
-  if ((size & (size - 1)) != 0) throw new IllegalArgumentException("buffer size must be a power of two")
+  if (size < 1) throw new IllegalArgumentException(s"buffer size must be positive (was: $size)")
+  if ((size & (size - 1)) != 0) throw new IllegalArgumentException(s"buffer size must be a power of two (was: $size)")
 
   // TODO: buffer and batch sizing heuristics
   private var upstream: Subscription = _
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Modules.scala b/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
index 3f2966e751..cf6d853bb3 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
@@ -12,6 +12,7 @@ import org.reactivestreams._
 import scala.annotation.unchecked.uncheckedVariance
 import scala.concurrent.Promise
 import akka.event.Logging
+import akka.util.OptionVal
 
 /**
  * INTERNAL API
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Sinks.scala b/akka-stream/src/main/scala/akka/stream/impl/Sinks.scala
index e9e8476e4b..1d7fca3d27 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Sinks.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Sinks.scala
@@ -37,6 +37,7 @@ import scala.compat.java8.OptionConverters._
 import java.util.Optional
 
 import akka.event.Logging
+import akka.util.OptionVal
 
 /**
  * INTERNAL API
diff --git a/akka-stream/src/main/scala/akka/stream/impl/TraversalBuilder.scala b/akka-stream/src/main/scala/akka/stream/impl/TraversalBuilder.scala
index 38fbd5eff4..3e001afee1 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/TraversalBuilder.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/TraversalBuilder.scala
@@ -353,7 +353,7 @@ final case class CompletedTraversalBuilder(
   inSlots:        Int,
   inToOffset:     Map[InPort, Int],
   attributes:     Attributes,
-  islandTag:      Option[IslandTag] = None) extends TraversalBuilder {
+  islandTag:      OptionVal[IslandTag] = OptionVal.None) extends TraversalBuilder {
 
   override def add[A, B, C](submodule: TraversalBuilder, shape: Shape, combineMat: (A, B) ⇒ C): TraversalBuilder = {
     val key = new BuilderKey
@@ -367,8 +367,8 @@ final case class CompletedTraversalBuilder(
 
   override def traversal: Traversal = {
     val withIsland = islandTag match {
-      case Some(tag) ⇒ EnterIsland(tag).concat(traversalSoFar).concat(ExitIsland)
-      case None      ⇒ traversalSoFar
+      case OptionVal.Some(tag) ⇒ EnterIsland(tag).concat(traversalSoFar).concat(ExitIsland)
+      case _                   ⇒ traversalSoFar
     }
 
     if (attributes eq Attributes.none) withIsland
@@ -392,8 +392,8 @@ final case class CompletedTraversalBuilder(
 
   override def makeIsland(islandTag: IslandTag): TraversalBuilder =
     this.islandTag match {
-      case None    ⇒ copy(islandTag = Some(islandTag))
-      case Some(_) ⇒ this
+      case OptionVal.None    ⇒ copy(islandTag = OptionVal(islandTag))
+      case OptionVal.Some(_) ⇒ this
     }
 
   override def assign(out: OutPort, relativeSlot: Int): TraversalBuilder =
@@ -518,10 +518,10 @@ object LinearTraversalBuilder {
         else empty().append(linear, combine)
 
       case completed: CompletedTraversalBuilder ⇒
-        val inOpt = shape.inlets.headOption
+        val inOpt = OptionVal(shape.inlets.headOption.orNull)
         val inOffs = inOpt match {
-          case Some(in) ⇒ completed.offsetOf(in)
-          case None     ⇒ 0
+          case OptionVal.Some(in) ⇒ completed.offsetOf(in)
+          case OptionVal.None     ⇒ 0
         }
 
         LinearTraversalBuilder(
@@ -534,11 +534,11 @@ object LinearTraversalBuilder {
           Attributes.none)
 
       case composite ⇒
-        val inOpt = shape.inlets.headOption
+        val inOpt = OptionVal(shape.inlets.headOption.orNull)
         val out = shape.outlets.head // Cannot be empty, otherwise it would be a CompletedTraversalBuilder
         val inOffs = inOpt match {
-          case Some(in) ⇒ composite.offsetOf(in)
-          case None     ⇒ 0
+          case OptionVal.Some(in) ⇒ composite.offsetOf(in)
+          case OptionVal.None     ⇒ 0
         }
 
         LinearTraversalBuilder(
@@ -640,6 +640,11 @@ final case class LinearTraversalBuilder(
             pendingBuilder = OptionVal.None, beforeBuilder = EmptyTraversal)
         case OptionVal.None ⇒
           copy(inPort = OptionVal.None, outPort = OptionVal.None, traversalSoFar = rewireLastOutTo(traversalSoFar, inOffset))
+        case OptionVal.None ⇒
+          copy(
+            inPort = OptionVal.None,
+            outPort = OptionVal.None,
+            traversalSoFar = rewireLastOutTo(traversalSoFar, inOffset))
       }
     } else
       throw new IllegalArgumentException(s"The ports $in and $out cannot be accessed in this builder.")
@@ -681,6 +686,9 @@ final case class LinearTraversalBuilder(
             beforeBuilder = EmptyTraversal)
         case OptionVal.None ⇒
           copy(outPort = OptionVal.None, traversalSoFar = rewireLastOutTo(traversalSoFar, relativeSlot))
+          copy(
+            outPort = OptionVal.None,
+            traversalSoFar = rewireLastOutTo(traversalSoFar, relativeSlot))
       }
     } else
       throw new IllegalArgumentException(s"Port $out cannot be assigned in this builder")
@@ -977,7 +985,7 @@ final case class CompositeTraversalBuilder(
   outOwners:          Map[OutPort, BuilderKey]          = Map.empty,
   unwiredOuts:        Int                               = 0,
   attributes:         Attributes,
-  islandTag:          IslandTag                         = null) extends TraversalBuilder {
+  islandTag:          OptionVal[IslandTag]              = OptionVal.None) extends TraversalBuilder {
 
   override def toString: String =
     s"""
@@ -1020,7 +1028,10 @@ final case class CompositeTraversalBuilder(
         remaining = remaining.tail
       }
 
-      val finalTraversal = if (islandTag == null) traversal else EnterIsland(islandTag).concat(traversal).concat(ExitIsland)
+      val finalTraversal = islandTag match {
+        case OptionVal.None      ⇒ traversal
+        case OptionVal.Some(tag) ⇒ EnterIsland(tag).concat(traversal).concat(ExitIsland)
+      }
 
       // The CompleteTraversalBuilder only keeps the minimum amount of necessary information that is needed for it
       // to be embedded in a larger graph, making partial graph reuse much more efficient.
@@ -1159,9 +1170,9 @@ final case class CompositeTraversalBuilder(
   }
 
   override def makeIsland(islandTag: IslandTag): TraversalBuilder = {
-    if (this.islandTag eq null)
-      copy(islandTag = islandTag)
-    else
-      this // Wrapping with an island, then immediately re-wrapping makes the second island empty, so can be omitted
+    this.islandTag match {
+      case OptionVal.None ⇒ copy(islandTag = OptionVal(islandTag))
+      case _              ⇒ this // Wrapping with an island, then immediately re-wrapping makes the second island empty, so can be omitted
+    }
   }
 }
diff --git a/akka-stream/src/main/scala/akka/stream/impl/io/TlsModule.scala b/akka-stream/src/main/scala/akka/stream/impl/io/TlsModule.scala
index 0bf03b351f..3817a0fe1a 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/io/TlsModule.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/io/TlsModule.scala
@@ -8,7 +8,7 @@ import akka.stream._
 import akka.stream.impl.StreamLayout.AtomicModule
 import akka.stream.TLSProtocol._
 import akka.stream.impl.{ TlsModuleIslandTag, TraversalBuilder }
-import akka.util.ByteString
+import akka.util.{ ByteString, OptionVal }
 
 import scala.util.Try
 
diff --git a/akka-stream/src/main/scala/akka/stream/stage/GraphStage.scala b/akka-stream/src/main/scala/akka/stream/stage/GraphStage.scala
index 68a101b1f8..5b3df91a2a 100644
--- a/akka-stream/src/main/scala/akka/stream/stage/GraphStage.scala
+++ b/akka-stream/src/main/scala/akka/stream/stage/GraphStage.scala
@@ -14,7 +14,7 @@ import akka.japi.function.{ Effect, Procedure }
 import akka.stream._
 import akka.stream.impl.StreamLayout.AtomicModule
 import akka.stream.impl.fusing.{ GraphInterpreter, GraphStageModule, SubSink, SubSource }
-import akka.stream.impl.{ ReactiveStreamsCompliance, TraversalBuilder }
+import akka.stream.impl.{ EmptyTraversal, LinearTraversalBuilder, ReactiveStreamsCompliance, TraversalBuilder }
 
 import scala.collection.mutable.ArrayBuffer
 import scala.collection.{ immutable, mutable }