diff --git a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSpec.scala
index a0299b90d0..da05c2e2c4 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSpec.scala
@@ -3,6 +3,7 @@
  */
 package akka.stream.impl.fusing
 
+import akka.stream.impl.ConstantFun
 import akka.stream.stage._
 import akka.stream.testkit.AkkaSpec
 import akka.testkit.EventFilter
@@ -241,10 +242,11 @@ class InterpreterSpec extends AkkaSpec with GraphInterpreterSpecKit {
       lastEvents() should be(Set(OnNext(Vector(3)), OnComplete))
     }
 
-    "implement conflate" in new OneBoundedSetup[Int](Seq(Conflate(
+    "implement batch (conflate)" in new OneBoundedSetup[Int](Batch(
+      1L,
+      ConstantFun.zeroLong,
       (in: Int) ⇒ in,
-      (agg: Int, x: Int) ⇒ agg + x,
-      stoppingDecider))) {
+      (agg: Int, x: Int) ⇒ agg + x)) {
 
       lastEvents() should be(Set(RequestOne))
 
@@ -299,15 +301,17 @@ class InterpreterSpec extends AkkaSpec with GraphInterpreterSpecKit {
       lastEvents() should be(Set(OnComplete))
     }
 
-    "work with conflate-conflate" in new OneBoundedSetup[Int](Seq(
-      Conflate(
+    "work with batch-batch (conflate-conflate)" in new OneBoundedSetup[Int](
+      Batch(
+        1L,
+        ConstantFun.zeroLong,
         (in: Int) ⇒ in,
-        (agg: Int, x: Int) ⇒ agg + x,
-        stoppingDecider),
-      Conflate(
+        (agg: Int, x: Int) ⇒ agg + x),
+      Batch(
+        1L,
+        ConstantFun.zeroLong,
         (in: Int) ⇒ in,
-        (agg: Int, x: Int) ⇒ agg + x,
-        stoppingDecider))) {
+        (agg: Int, x: Int) ⇒ agg + x)) {
 
       lastEvents() should be(Set(RequestOne))
 
@@ -370,11 +374,12 @@ class InterpreterSpec extends AkkaSpec with GraphInterpreterSpecKit {
       lastEvents() should be(Set(OnComplete, OnNext(12)))
     }
 
-    "implement conflate-expand" in new OneBoundedSetup[Int](
-      Conflate(
+    "implement batch-expand (conflate-expand)" in new OneBoundedSetup[Int](
+      Batch(
+        1L,
+        ConstantFun.zeroLong,
         (in: Int) ⇒ in,
-        (agg: Int, x: Int) ⇒ agg + x,
-        stoppingDecider).toGS,
+        (agg: Int, x: Int) ⇒ agg + x),
       new Expand(Iterator.continually(_: Int))) {
 
       lastEvents() should be(Set(RequestOne))
@@ -404,12 +409,13 @@ class InterpreterSpec extends AkkaSpec with GraphInterpreterSpecKit {
       lastEvents() should be(Set(Cancel))
     }
 
-    "implement doubler-conflate" in new OneBoundedSetup[Int](Seq(
-      Doubler(),
-      Conflate(
+    "implement doubler-conflate (doubler-batch)" in new OneBoundedSetup[Int](
+      Doubler().toGS,
+      Batch(
+        1L,
+        ConstantFun.zeroLong,
         (in: Int) ⇒ in,
-        (agg: Int, x: Int) ⇒ agg + x,
-        stoppingDecider))) {
+        (agg: Int, x: Int) ⇒ agg + x)) {
       lastEvents() should be(Set(RequestOne))
 
       upstream.onNext(1)
diff --git a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterStressSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterStressSpec.scala
index f443c112de..13209fcb3e 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterStressSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterStressSpec.scala
@@ -4,6 +4,7 @@
 package akka.stream.impl.fusing
 
 import akka.NotUsed
+import akka.stream.impl.ConstantFun
 import akka.stream.{ Attributes, Shape, Supervision }
 import akka.stream.stage.AbstractStage.PushPullGraphStage
 import akka.stream.stage.GraphStageWithMaterializedValue
@@ -100,25 +101,26 @@ class InterpreterStressSpec extends AkkaSpec with GraphInterpreterSpecKit {
 
     }
 
-    "work with a massive chain of conflates by overflowing to the heap" in new OneBoundedSetup[Int](Vector.fill(chainLength / 10)(Conflate(
-      (in: Int) ⇒ in,
-      (agg: Int, in: Int) ⇒ agg + in,
-      Supervision.stoppingDecider))) {
+    "work with a massive chain of batches by overflowing to the heap" in {
 
-      lastEvents() should be(Set(RequestOne))
+      val batch = Batch(
+        0L,
+        ConstantFun.zeroLong,
+        (in: Int) ⇒ in,
+        (agg: Int, in: Int) ⇒ agg + in)
+
+      new OneBoundedSetup[Int](Vector.fill(chainLength / 10)(batch): _*) {
 
-      var i = 0
-      while (i < repetition) {
-        upstream.onNext(1)
         lastEvents() should be(Set(RequestOne))
-        i += 1
+
+        var i = 0
+        while (i < repetition) {
+          upstream.onNext(1)
+          lastEvents() should be(Set(RequestOne))
+          i += 1
+        }
       }
-
-      downstream.requestOne()
-      lastEvents() should be(Set(OnNext(repetition)))
-
     }
-
   }
 
 }
diff --git a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSupervisionSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSupervisionSpec.scala
index e98dd9693d..90f08118e4 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSupervisionSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/impl/fusing/InterpreterSupervisionSpec.scala
@@ -387,70 +387,6 @@ class InterpreterSupervisionSpec extends AkkaSpec with GraphInterpreterSpecKit {
       lastEvents() should be(Set(OnNext(25))) // 1 + 4 + 20
     }
 
-    "restart when Conflate `seed` throws" in new OneBoundedSetup[Int](Seq(Conflate(
-      (in: Int) ⇒ if (in == 1) throw TE else in,
-      (agg: Int, x: Int) ⇒ agg + x,
-      restartingDecider))) {
-
-      lastEvents() should be(Set(RequestOne))
-
-      downstream.requestOne()
-      lastEvents() should be(Set.empty)
-
-      upstream.onNext(0)
-      lastEvents() should be(Set(OnNext(0), RequestOne))
-
-      upstream.onNext(1) // boom
-      lastEvents() should be(Set(RequestOne))
-
-      upstream.onNext(2)
-      lastEvents() should be(Set(RequestOne))
-
-      upstream.onNext(10)
-      lastEvents() should be(Set(RequestOne))
-
-      downstream.requestOne()
-      lastEvents() should be(Set(OnNext(12))) // note that 1 has been discarded
-
-      downstream.requestOne()
-      lastEvents() should be(Set.empty)
-    }
-
-    "restart when Conflate `aggregate` throws" in new OneBoundedSetup[Int](Seq(Conflate(
-      (in: Int) ⇒ in,
-      (agg: Int, x: Int) ⇒ if (x == 2) throw TE else agg + x,
-      restartingDecider))) {
-
-      lastEvents() should be(Set(RequestOne))
-
-      downstream.requestOne()
-      lastEvents() should be(Set.empty)
-
-      upstream.onNext(0)
-      lastEvents() should be(Set(OnNext(0), RequestOne))
-
-      upstream.onNext(1)
-      lastEvents() should be(Set(RequestOne))
-
-      upstream.onNext(2) // boom
-      lastEvents() should be(Set(RequestOne))
-
-      upstream.onNext(10)
-      lastEvents() should be(Set(RequestOne))
-
-      downstream.requestOne()
-      lastEvents() should be(Set(OnNext(10))) // note that 1 and 2 has been discarded
-
-      downstream.requestOne()
-      lastEvents() should be(Set.empty)
-
-      upstream.onNext(4)
-      lastEvents() should be(Set(OnNext(4), RequestOne))
-
-      downstream.cancel()
-      lastEvents() should be(Set(Cancel))
-    }
-
     "fail when Expand `seed` throws" in new OneBoundedSetup[Int](
       new Expand((in: Int) ⇒ if (in == 2) throw TE else Iterator(in) ++ Iterator.continually(-math.abs(in)))) {
 
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowConflateSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowConflateSpec.scala
index 9d951c5fb6..152bd2d8c4 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowConflateSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowConflateSpec.scala
@@ -3,10 +3,15 @@
  */
 package akka.stream.scaladsl
 
+import akka.stream.ActorAttributes.supervisionStrategy
+import akka.stream.Attributes.inputBuffer
+import akka.stream.Supervision.{ resumingDecider, restartingDecider }
+import akka.stream.testkit.Utils.TE
+
 import scala.concurrent.Await
 import scala.concurrent.duration._
 import scala.concurrent.forkjoin.ThreadLocalRandom
-import akka.stream.{ OverflowStrategy, ActorMaterializer, ActorMaterializerSettings }
+import akka.stream._
 import akka.stream.testkit._
 
 class FlowConflateSpec extends AkkaSpec {
@@ -135,6 +140,103 @@ class FlowConflateSpec extends AkkaSpec {
       Await.result(future, 3.seconds) should be((1 to 50).sum)
     }
 
+    "restart when `seed` throws and a restartingDecider is used" in {
+      val sourceProbe = TestPublisher.probe[Int]()
+      val sinkProbe = TestSubscriber.probe[Int]()
+
+      val future = Source.fromPublisher(sourceProbe)
+        .conflateWithSeed(seed = i ⇒
+          if (i % 2 == 0) throw TE("I hate even seed numbers") else i)(aggregate = (sum, i) ⇒ sum + i)
+        .withAttributes(supervisionStrategy(restartingDecider))
+        .to(Sink.fromSubscriber(sinkProbe))
+        .withAttributes(inputBuffer(initial = 1, max = 1))
+        .run()
+
+      val sub = sourceProbe.expectSubscription()
+      val sinkSub = sinkProbe.expectSubscription()
+      // push the first value
+      sub.expectRequest(1)
+      sub.sendNext(1)
+
+      // and consume it, so that the next element
+      // will trigger seed
+      sinkSub.request(1)
+      sinkProbe.expectNext(1)
+
+      sub.expectRequest(1)
+      sub.sendNext(2)
+      sub.expectRequest(1)
+      sub.sendNext(3)
+
+      // now we should have lost the 2 and the accumulated state
+      sinkSub.request(1)
+      sinkProbe.expectNext(3)
+    }
+
+    "restart when `aggregate` throws and a restartingDecider is used" in {
+      val conflate = Flow[String]
+        .conflateWithSeed(seed = i ⇒ i)((state, elem) ⇒
+          if (elem == "two") throw TE("two is a three letter word")
+          else state + elem)
+        .withAttributes(supervisionStrategy(restartingDecider))
+
+      val sourceProbe = TestPublisher.probe[String]()
+      val sinkProbe = TestSubscriber.probe[String]()
+
+      Source.fromPublisher(sourceProbe)
+        .via(conflate)
+        .to(Sink.fromSubscriber(sinkProbe))
+        .withAttributes(inputBuffer(initial = 4, max = 4))
+        .run()
+
+      val sub = sourceProbe.expectSubscription()
+      sub.expectRequest(4)
+      sub.sendNext("one")
+      sub.sendNext("two")
+      sub.sendNext("three")
+      sub.sendComplete()
+
+      // "one" should be lost
+      sinkProbe.requestNext() shouldEqual ("three")
+
+    }
+
+    "resume when `aggregate` throws and a resumingDecider is used" in {
+
+      val sourceProbe = TestPublisher.probe[Int]()
+      val sinkProbe = TestSubscriber.probe[Vector[Int]]()
+
+      val future = Source.fromPublisher(sourceProbe)
+        .conflateWithSeed(seed = i ⇒ Vector(i))((state, elem) ⇒
+          if (elem == 2) throw TE("three is a four letter word") else state :+ elem)
+        .withAttributes(supervisionStrategy(resumingDecider))
+        .to(Sink.fromSubscriber(sinkProbe))
+        .withAttributes(inputBuffer(initial = 1, max = 1))
+        .run()
+
+      val sub = sourceProbe.expectSubscription()
+      val sinkSub = sinkProbe.expectSubscription()
+      // push the first three values, the third will trigger
+      // the exception
+      sub.expectRequest(1)
+      sub.sendNext(1)
+
+      // causing the 1 to get thrown away
+      sub.expectRequest(1)
+      sub.sendNext(2)
+
+      sub.expectRequest(1)
+      sub.sendNext(3)
+
+      sub.expectRequest(1)
+      sub.sendNext(4)
+
+      // and consume it, so that the next element
+      // will trigger seed
+      sinkSub.request(1)
+      sinkProbe.expectNext(Vector(1, 3, 4))
+    }
+
   }
 
 }
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Stages.scala b/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
index f9881314de..771664d742 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
@@ -205,10 +205,6 @@ private[stream] object Stages {
     override def create(attr: Attributes): Stage[T, T] = fusing.Buffer(size, overflowStrategy)
   }
 
-  final case class Conflate[In, Out](seed: In ⇒ Out, aggregate: (Out, In) ⇒ Out, attributes: Attributes = conflate) extends SymbolicStage[In, Out] {
-    override def create(attr: Attributes): Stage[In, Out] = fusing.Conflate(seed, aggregate, supervision(attr))
-  }
-
   final case class MapConcat[In, Out](f: In ⇒ immutable.Iterable[Out], attributes: Attributes = mapConcat) extends SymbolicStage[In, Out] {
     override def create(attr: Attributes): Stage[In, Out] = fusing.MapConcat(f, supervision(attr))
   }
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 a2706ce4d0..669bff29c6 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
@@ -432,50 +432,6 @@ private[akka] final case class Completed[T]() extends PushPullStage[T, T] {
   override def onPull(ctx: Context[T]): SyncDirective = ctx.finish()
 }
 
-/**
- * INTERNAL API
- */
-private[akka] final case class Conflate[In, Out](seed: In ⇒ Out, aggregate: (Out, In) ⇒ Out,
-                                                 decider: Supervision.Decider) extends DetachedStage[In, Out] {
-  private var agg: Any = null
-
-  override def onPush(elem: In, ctx: DetachedContext[Out]): UpstreamDirective = {
-    agg =
-      if (agg == null) seed(elem)
-      else aggregate(agg.asInstanceOf[Out], elem)
-
-    if (!ctx.isHoldingDownstream) ctx.pull()
-    else {
-      val result = agg.asInstanceOf[Out]
-      agg = null
-      ctx.pushAndPull(result)
-    }
-  }
-
-  override def onPull(ctx: DetachedContext[Out]): DownstreamDirective = {
-    if (ctx.isFinishing) {
-      if (agg == null) ctx.finish()
-      else {
-        val result = agg.asInstanceOf[Out]
-        agg = null
-        ctx.pushAndFinish(result)
-      }
-    } else if (agg == null) ctx.holdDownstream()
-    else {
-      val result = agg.asInstanceOf[Out]
-      if (result == null) throw new NullPointerException
-      agg = null
-      ctx.push(result)
-    }
-  }
-
-  override def onUpstreamFinish(ctx: DetachedContext[Out]): TerminationDirective = ctx.absorbTermination()
-
-  override def decide(t: Throwable): Supervision.Directive = decider(t)
-
-  override def restart(): Conflate[In, Out] = copy()
-}
-
 /**
  * INTERNAL API
  */
@@ -488,6 +444,9 @@ private[akka] final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, se
   override val shape: FlowShape[In, Out] = FlowShape.of(in, out)
 
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) {
+
+    val decider = inheritedAttributes.getAttribute(classOf[SupervisionStrategy]).map(_.decider).getOrElse(Supervision.stoppingDecider)
+
     private var agg: Out = null.asInstanceOf[Out]
     private var left: Long = max
     private var pending: In = null.asInstanceOf[In]
@@ -496,10 +455,18 @@ private[akka] final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, se
       push(out, agg)
       left = max
       if (pending != null) {
-        val elem = pending
-        agg = seed(elem)
-        left -= costFn(elem)
-        pending = null.asInstanceOf[In]
+        try {
+          agg = seed(pending)
+          left -= costFn(pending)
+          pending = null.asInstanceOf[In]
+        } catch {
+          case NonFatal(ex) ⇒ decider(ex) match {
+            case Supervision.Stop    ⇒ failStage(ex)
+            case Supervision.Restart ⇒ restartState()
+            case Supervision.Resume ⇒
+              pending = null.asInstanceOf[In]
+          }
+        }
       } else {
         agg = null.asInstanceOf[Out]
       }
@@ -512,14 +479,33 @@ private[akka] final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, se
       override def onPush(): Unit = {
         val elem = grab(in)
         val cost = costFn(elem)
+
         if (agg == null) {
-          left -= cost
-          agg = seed(elem)
+          try {
+            agg = seed(elem)
+            left -= cost
+          } catch {
+            case NonFatal(ex) ⇒ decider(ex) match {
+              case Supervision.Stop ⇒ failStage(ex)
+              case Supervision.Restart ⇒
+                restartState()
+              case Supervision.Resume ⇒
+            }
+          }
         } else if (left < cost) {
           pending = elem
         } else {
-          left -= cost
-          agg = aggregate(agg, elem)
+          try {
+            agg = aggregate(agg, elem)
+            left -= cost
+          } catch {
+            case NonFatal(ex) ⇒ decider(ex) match {
+              case Supervision.Stop ⇒ failStage(ex)
+              case Supervision.Restart ⇒
+                restartState()
+              case Supervision.Resume ⇒
+            }
+          }
         }
 
         if (isAvailable(out)) flush()
@@ -541,15 +527,32 @@ private[akka] final case class Batch[In, Out](max: Long, costFn: In ⇒ Long, se
           push(out, agg)
           if (pending == null) completeStage()
           else {
-            agg = seed(pending)
+            try {
+              agg = seed(pending)
+            } catch {
+              case NonFatal(ex) ⇒ decider(ex) match {
+                case Supervision.Stop   ⇒ failStage(ex)
+                case Supervision.Resume ⇒
+                case Supervision.Restart ⇒
+                  restartState()
+                  if (!hasBeenPulled(in)) pull(in)
+              }
+            }
             pending = null.asInstanceOf[In]
           }
         } else {
           flush()
           if (!hasBeenPulled(in)) pull(in)
         }
+
       }
     })
+
+    private def restartState(): Unit = {
+      agg = null.asInstanceOf[Out]
+      left = max
+      pending = null.asInstanceOf[In]
+    }
   }
 }
 
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
index fa2956f215..ee3deacd7b 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
@@ -934,9 +934,8 @@ trait FlowOps[+Out, +Mat] {
    *
    * See also [[FlowOps.conflate]], [[FlowOps.limit]], [[FlowOps.limitWeighted]] [[FlowOps.batch]] [[FlowOps.batchWeighted]]
    */
-  def conflateWithSeed[S](seed: Out ⇒ S)(aggregate: (S, Out) ⇒ S): Repr[S] = andThen(Conflate(seed, aggregate))
-  //FIXME: conflate can be expressed as a batch
-  //via(Batch(1L, ConstantFun.zeroLong, seed, aggregate).withAttributes(DefaultAttributes.conflate))
+  def conflateWithSeed[S](seed: Out ⇒ S)(aggregate: (S, Out) ⇒ S): Repr[S] =
+    via(Batch(1L, ConstantFun.zeroLong, seed, aggregate).withAttributes(DefaultAttributes.conflate))