diff --git a/akka-stream/src/main/scala/akka/stream/impl/Throttle.scala b/akka-stream/src/main/scala/akka/stream/impl/Throttle.scala
index 577ea899e0..44cd31ee6c 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Throttle.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Throttle.scala
@@ -15,11 +15,11 @@ import scala.concurrent.duration.{ FiniteDuration, _ }
  * INTERNAL API
  */
 class Throttle[T](
-  cost:            Int,
-  per:             FiniteDuration,
-  maximumBurst:    Int,
-  costCalculation: (T) ⇒ Int,
-  mode:            ThrottleMode)
+  val cost:            Int,
+  val per:             FiniteDuration,
+  val maximumBurst:    Int,
+  val costCalculation: (T) ⇒ Int,
+  val mode:            ThrottleMode)
   extends SimpleLinearGraphStage[T] {
   require(cost > 0, "cost must be > 0")
   require(per.toNanos > 0, "per time must be > 0")
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Timers.scala b/akka-stream/src/main/scala/akka/stream/impl/Timers.scala
index daa0fea687..5706fc0e25 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Timers.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Timers.scala
@@ -31,7 +31,7 @@ object Timers {
       TimeUnit.NANOSECONDS)
   }
 
-  final class Initial[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+  final class Initial[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
     override def initialAttributes = DefaultAttributes.initial
 
     override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
@@ -58,7 +58,7 @@ object Timers {
 
   }
 
-  final class Completion[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+  final class Completion[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
     override def initialAttributes = DefaultAttributes.completion
 
     override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
@@ -79,7 +79,7 @@ object Timers {
 
   }
 
-  final class Idle[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+  final class Idle[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
     override def initialAttributes = DefaultAttributes.idle
 
     override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
@@ -106,7 +106,7 @@ object Timers {
 
   }
 
-  final class BackpressureTimeout[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+  final class BackpressureTimeout[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
     override def initialAttributes = DefaultAttributes.backpressureTimeout
 
     override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
@@ -208,7 +208,7 @@ object Timers {
 
   }
 
-  final class IdleInject[I, O >: I](val timeout: FiniteDuration, inject: () ⇒ O) extends GraphStage[FlowShape[I, O]] {
+  final class IdleInject[I, O >: I](val timeout: FiniteDuration, val inject: () ⇒ O) extends GraphStage[FlowShape[I, O]] {
     val in: Inlet[I] = Inlet("IdleInject.in")
     val out: Outlet[O] = Outlet("IdleInject.out")
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphStages.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphStages.scala
index 4e2fe7e682..0a08583d84 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphStages.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphStages.scala
@@ -221,7 +221,7 @@ object GraphStages {
     }
   }
 
-  final class TickSource[T](initialDelay: FiniteDuration, interval: FiniteDuration, tick: T)
+  final class TickSource[T](val initialDelay: FiniteDuration, val interval: FiniteDuration, val tick: T)
     extends GraphStageWithMaterializedValue[SourceShape[T], Cancellable] {
     override val shape = SourceShape(Outlet[T]("TickSource.out"))
     val out = shape.out
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
index 3103712952..da46440efd 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
@@ -522,7 +522,7 @@ final case class Grouped[T](n: Int) extends GraphStage[FlowShape[T, immutable.Se
 /**
  * INTERNAL API
  */
-final case class LimitWeighted[T](n: Long, costFn: T ⇒ Long) extends GraphStage[FlowShape[T, T]] {
+final case class LimitWeighted[T](val n: Long, val costFn: T ⇒ Long) extends GraphStage[FlowShape[T, T]] {
   val in = Inlet[T]("LimitWeighted.in")
   val out = Outlet[T]("LimitWeighted.out")
   override val shape = FlowShape(in, out)
@@ -554,7 +554,7 @@ final case class LimitWeighted[T](n: Long, costFn: T ⇒ Long) extends GraphStag
 /**
  * INTERNAL API
  */
-final case class Sliding[T](n: Int, step: Int) extends GraphStage[FlowShape[T, immutable.Seq[T]]] {
+final case class Sliding[T](val n: Int, val step: Int) extends GraphStage[FlowShape[T, immutable.Seq[T]]] {
   require(n > 0, "n must be greater than 0")
   require(step > 0, "step must be greater than 0")
 
@@ -672,7 +672,7 @@ final case class Buffer[T](size: Int, overflowStrategy: OverflowStrategy) extend
 /**
  * INTERNAL API
  */
-final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, seed: In ⇒ Out, aggregate: (Out, In) ⇒ Out)
+final case class Batch[In, Out](val max: Long, val costFn: In ⇒ Long, val seed: In ⇒ Out, val aggregate: (Out, In) ⇒ Out)
   extends GraphStage[FlowShape[In, Out]] {
 
   val in = Inlet[In]("Batch.in")
@@ -798,7 +798,7 @@ final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, seed: In ⇒ Out
 /**
  * INTERNAL API
  */
-final class Expand[In, Out](extrapolate: In ⇒ Iterator[Out]) extends GraphStage[FlowShape[In, Out]] {
+final class Expand[In, Out](val extrapolate: In ⇒ Iterator[Out]) extends GraphStage[FlowShape[In, Out]] {
   private val in = Inlet[In]("expand.in")
   private val out = Outlet[Out]("expand.out")
 
@@ -1127,7 +1127,7 @@ private[stream] object TimerKeys {
   case object GroupedWithinTimerKey
 }
 
-final class GroupedWithin[T](n: Int, d: FiniteDuration) extends GraphStage[FlowShape[T, immutable.Seq[T]]] {
+final class GroupedWithin[T](val n: Int, val d: FiniteDuration) extends GraphStage[FlowShape[T, immutable.Seq[T]]] {
   require(n > 0, "n must be greater than 0")
   require(d > Duration.Zero)
 
@@ -1203,7 +1203,7 @@ final class GroupedWithin[T](n: Int, d: FiniteDuration) extends GraphStage[FlowS
   }
 }
 
-final class Delay[T](d: FiniteDuration, strategy: DelayOverflowStrategy) extends SimpleLinearGraphStage[T] {
+final class Delay[T](val d: FiniteDuration, val strategy: DelayOverflowStrategy) extends SimpleLinearGraphStage[T] {
   private[this] def timerName = "DelayedTimer"
   override def initialAttributes: Attributes = DefaultAttributes.delay
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new TimerGraphStageLogic(shape) {
@@ -1289,7 +1289,7 @@ final class Delay[T](d: FiniteDuration, strategy: DelayOverflowStrategy) extends
   override def toString = "Delay"
 }
 
-final class TakeWithin[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+final class TakeWithin[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
 
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new TimerGraphStageLogic(shape) {
     setHandler(in, new InHandler {
@@ -1309,7 +1309,7 @@ final class TakeWithin[T](timeout: FiniteDuration) extends SimpleLinearGraphStag
   override def toString = "TakeWithin"
 }
 
-final class DropWithin[T](timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
+final class DropWithin[T](val timeout: FiniteDuration) extends SimpleLinearGraphStage[T] {
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new TimerGraphStageLogic(shape) {
 
     private var allow = false
@@ -1335,7 +1335,7 @@ final class DropWithin[T](timeout: FiniteDuration) extends SimpleLinearGraphStag
 /**
  * INTERNAL API
  */
-final class Reduce[T](f: (T, T) ⇒ T) extends SimpleLinearGraphStage[T] {
+final class Reduce[T](val f: (T, T) ⇒ T) extends SimpleLinearGraphStage[T] {
   override def initialAttributes: Attributes = DefaultAttributes.reduce
 
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) with InHandler with OutHandler { self ⇒
@@ -1379,7 +1379,7 @@ private[stream] object RecoverWith {
   val InfiniteRetries = -1
 }
 
-final class RecoverWith[T, M](maximumRetries: Int, pf: PartialFunction[Throwable, Graph[SourceShape[T], M]]) extends SimpleLinearGraphStage[T] {
+final class RecoverWith[T, M](val maximumRetries: Int, val pf: PartialFunction[Throwable, Graph[SourceShape[T], M]]) extends SimpleLinearGraphStage[T] {
   require(maximumRetries >= -1, "number of retries must be non-negative or equal to -1")
   override def initialAttributes = DefaultAttributes.recoverWith
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/StreamOfStreams.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/StreamOfStreams.scala
index f238a5eedd..43cc221160 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/StreamOfStreams.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/StreamOfStreams.scala
@@ -24,7 +24,7 @@ import scala.collection.JavaConversions._
 /**
  * INTERNAL API
  */
-final class FlattenMerge[T, M](breadth: Int) extends GraphStage[FlowShape[Graph[SourceShape[T], M], T]] {
+final class FlattenMerge[T, M](val breadth: Int) extends GraphStage[FlowShape[Graph[SourceShape[T], M], T]] {
   private val in = Inlet[Graph[SourceShape[T], M]]("flatten.in")
   private val out = Outlet[T]("flatten.out")
 
@@ -103,7 +103,7 @@ final class FlattenMerge[T, M](breadth: Int) extends GraphStage[FlowShape[Graph[
 /**
  * INTERNAL API
  */
-final class PrefixAndTail[T](n: Int) extends GraphStage[FlowShape[T, (immutable.Seq[T], Source[T, NotUsed])]] {
+final class PrefixAndTail[T](val n: Int) extends GraphStage[FlowShape[T, (immutable.Seq[T], Source[T, NotUsed])]] {
   val in: Inlet[T] = Inlet("PrefixAndTail.in")
   val out: Outlet[(immutable.Seq[T], Source[T, NotUsed])] = Outlet("PrefixAndTail.out")
   override val shape: FlowShape[T, (immutable.Seq[T], Source[T, NotUsed])] = FlowShape(in, out)
@@ -211,7 +211,7 @@ final class PrefixAndTail[T](n: Int) extends GraphStage[FlowShape[T, (immutable.
 /**
  * INTERNAL API
  */
-final class GroupBy[T, K](maxSubstreams: Int, keyFor: T ⇒ K) extends GraphStage[FlowShape[T, Source[T, NotUsed]]] {
+final class GroupBy[T, K](val maxSubstreams: Int, val keyFor: T ⇒ K) extends GraphStage[FlowShape[T, Source[T, NotUsed]]] {
   val in: Inlet[T] = Inlet("GroupBy.in")
   val out: Outlet[Source[T, NotUsed]] = Outlet("GroupBy.out")
   override val shape: FlowShape[T, Source[T, NotUsed]] = FlowShape(in, out)
@@ -403,7 +403,7 @@ object Split {
 /**
  * INTERNAL API
  */
-final class Split[T](decision: Split.SplitDecision, p: T ⇒ Boolean, substreamCancelStrategy: SubstreamCancelStrategy) extends GraphStage[FlowShape[T, Source[T, NotUsed]]] {
+final class Split[T](val decision: Split.SplitDecision, val p: T ⇒ Boolean, val substreamCancelStrategy: SubstreamCancelStrategy) extends GraphStage[FlowShape[T, Source[T, NotUsed]]] {
   val in: Inlet[T] = Inlet("Split.in")
   val out: Outlet[Source[T, NotUsed]] = Outlet("Split.out")
   override val shape: FlowShape[T, Source[T, NotUsed]] = FlowShape(in, out)
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala b/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala
index a57a6ac437..28d6ab58dd 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala
@@ -40,7 +40,7 @@ object Merge {
  *
  * '''Cancels when''' downstream cancels
  */
-final class Merge[T] private (val inputPorts: Int, val eagerComplete: Boolean) extends GraphStage[UniformFanInShape[T, T]] {
+final class Merge[T](val inputPorts: Int, val eagerComplete: Boolean) extends GraphStage[UniformFanInShape[T, T]] {
   // one input might seem counter intuitive but saves us from special handling in other places
   require(inputPorts >= 1, "A Merge must have one or more input ports")
 
@@ -146,7 +146,7 @@ object MergePreferred {
  *
  * A `Broadcast` has one `in` port and 2 or more `out` ports.
  */
-final class MergePreferred[T] private (val secondaryPorts: Int, val eagerComplete: Boolean) extends GraphStage[MergePreferred.MergePreferredShape[T]] {
+final class MergePreferred[T](val secondaryPorts: Int, val eagerComplete: Boolean) extends GraphStage[MergePreferred.MergePreferredShape[T]] {
   require(secondaryPorts >= 1, "A MergePreferred must have more than 0 secondary input ports")
 
   override def initialAttributes = DefaultAttributes.mergePreferred
@@ -258,7 +258,7 @@ object Interleave {
  * '''Cancels when''' downstream cancels
  *
  */
-final class Interleave[T] private (val inputPorts: Int, val segmentSize: Int, val eagerClose: Boolean) extends GraphStage[UniformFanInShape[T, T]] {
+final class Interleave[T](val inputPorts: Int, val segmentSize: Int, val eagerClose: Boolean) extends GraphStage[UniformFanInShape[T, T]] {
   require(inputPorts > 1, "input ports must be > 1")
   require(segmentSize > 0, "segmentSize must be > 0")
 
@@ -397,7 +397,7 @@ object Broadcast {
  *   If eagerCancel is enabled: when any downstream cancels; otherwise: when all downstreams cancel
  *
  */
-final class Broadcast[T](private val outputPorts: Int, eagerCancel: Boolean) extends GraphStage[UniformFanOutShape[T, T]] {
+final class Broadcast[T](val outputPorts: Int, val eagerCancel: Boolean) extends GraphStage[UniformFanOutShape[T, T]] {
   // one output might seem counter intuitive but saves us from special handling in other places
   require(outputPorts >= 1, "A Broadcast must have one or more output ports")
   val in: Inlet[T] = Inlet[T]("Broadcast.in")
@@ -496,7 +496,7 @@ object Partition {
  *   when all downstreams cancel
  */
 
-final class Partition[T](outputPorts: Int, partitioner: T ⇒ Int) extends GraphStage[UniformFanOutShape[T, T]] {
+final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int) extends GraphStage[UniformFanOutShape[T, T]] {
 
   val in: Inlet[T] = Inlet[T]("Partition.in")
   val out: Seq[Outlet[T]] = Seq.tabulate(outputPorts)(i ⇒ Outlet[T]("Partition.out" + i))
@@ -602,7 +602,7 @@ object Balance {
  *
  * '''Cancels when''' all downstreams cancel
  */
-final class Balance[T](val outputPorts: Int, waitForAllDownstreams: Boolean) extends GraphStage[UniformFanOutShape[T, T]] {
+final class Balance[T](val outputPorts: Int, val waitForAllDownstreams: Boolean) extends GraphStage[UniformFanOutShape[T, T]] {
   // one output might seem counter intuitive but saves us from special handling in other places
   require(outputPorts >= 1, "A Balance must have one or more output ports")
   val in: Inlet[T] = Inlet[T]("Balance.in")
@@ -870,7 +870,7 @@ object Concat {
  *
  * '''Cancels when''' downstream cancels
  */
-final class Concat[T](inputPorts: Int) extends GraphStage[UniformFanInShape[T, T]] {
+final class Concat[T](val inputPorts: Int) extends GraphStage[UniformFanInShape[T, T]] {
   require(inputPorts > 1, "A Concat must have more than 1 input ports")
   val in: immutable.IndexedSeq[Inlet[T]] = Vector.tabulate(inputPorts)(i ⇒ Inlet[T]("Concat.in" + i))
   val out: Outlet[T] = Outlet[T]("Concat.out")