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 e8086ac2c0..9270e591d5 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala
@@ -52,25 +52,16 @@ final class Merge[T] private (val inputPorts: Int, val eagerComplete: Boolean) e
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) {
     private var initialized = false
 
-    private val pendingQueue = Array.ofDim[Inlet[T]](inputPorts)
-    private var pendingHead = 0
-    private var pendingTail = 0
+    private val pendingQueue = FixedSizeBuffer[Inlet[T]](inputPorts)
+    private def pending: Boolean = pendingQueue.nonEmpty
 
     private var runningUpstreams = inputPorts
     private def upstreamsClosed = runningUpstreams == 0
 
-    private def pending: Boolean = pendingHead != pendingTail
-
     override def preStart(): Unit = in.foreach(tryPull)
 
-    private def enqueue(in: Inlet[T]): Unit = {
-      pendingQueue(pendingTail % inputPorts) = in
-      pendingTail += 1
-    }
-
     private def dequeueAndDispatch(): Unit = {
-      val in = pendingQueue(pendingHead % inputPorts)
-      pendingHead += 1
+      val in = pendingQueue.dequeue()
       push(out, grab(in))
       if (upstreamsClosed && !pending) completeStage()
       else tryPull(in)
@@ -84,7 +75,7 @@ final class Merge[T] private (val inputPorts: Int, val eagerComplete: Boolean) e
               push(out, grab(i))
               tryPull(i)
             }
-          } else enqueue(i)
+          } else pendingQueue.enqueue(i)
         }
 
         override def onUpstreamFinish() =
@@ -1009,7 +1000,7 @@ object GraphDSL extends GraphApply {
     }
 
     private class PortOpsImpl[+Out](override val outlet: Outlet[Out @uncheckedVariance], b: Builder[_])
-      extends PortOps[Out] {
+        extends PortOps[Out] {
 
       override def withAttributes(attr: Attributes): Repr[Out] = throw settingAttrNotSupported
       override def addAttributes(attr: Attributes): Repr[Out] = throw settingAttrNotSupported