diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/ActorRefBackpressureSinkStage.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/ActorRefBackpressureSinkStage.scala
index c5224843c5..47f3676638 100644
--- a/stream/src/main/scala/org/apache/pekko/stream/impl/ActorRefBackpressureSinkStage.scala
+++ b/stream/src/main/scala/org/apache/pekko/stream/impl/ActorRefBackpressureSinkStage.scala
@@ -45,7 +45,7 @@ import pekko.stream.stage._
       private val maxBuffer = inheritedAttributes.get[InputBuffer](InputBuffer(16, 16)).max
       require(maxBuffer > 0, "Buffer size must be greater than 0")
 
-      private val buffer: util.Deque[In] = new util.ArrayDeque[In]()
+      private val buffer: util.ArrayDeque[In] = new util.ArrayDeque[In]()
       private var acknowledgementReceived = false
       private var completeReceived = false
       private var completionSignalled = false
@@ -75,7 +75,7 @@ import pekko.stream.stage._
       }
 
       private def dequeueAndSend(): Unit = {
-        ref ! messageAdapter(self)(buffer.poll())
+        ref ! messageAdapter(self)(buffer.pollFirst())
       }
 
       private def finish(): Unit = {
@@ -85,7 +85,7 @@ import pekko.stream.stage._
       }
 
       def onPush(): Unit = {
-        buffer.offer(grab(in))
+        buffer.offerLast(grab(in))
         if (acknowledgementReceived) {
           dequeueAndSend()
           acknowledgementReceived = false
diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/PhasedFusingActorMaterializer.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/PhasedFusingActorMaterializer.scala
index c130aed607..fbff399df9 100644
--- a/stream/src/main/scala/org/apache/pekko/stream/impl/PhasedFusingActorMaterializer.scala
+++ b/stream/src/main/scala/org/apache/pekko/stream/impl/PhasedFusingActorMaterializer.scala
@@ -524,7 +524,7 @@ private final case class SavedIslandData(
             if (Debug) println(s"PUSH: $matValue => $matValueStack")
 
           case Concat(first, next) =>
-            if (next ne EmptyTraversal) traversalStack.add(next)
+            if (next ne EmptyTraversal) traversalStack.addLast(next)
             nextStep = first
           case Pop =>
             val popped = matValueStack.removeLast()
diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/ActorGraphInterpreter.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/ActorGraphInterpreter.scala
index ad5f3b325a..d4f6bced23 100644
--- a/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/ActorGraphInterpreter.scala
+++ b/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/ActorGraphInterpreter.scala
@@ -796,7 +796,7 @@ import org.reactivestreams.Subscription
     else if (currentLimit == 0) {
       self ! Resume
     } else {
-      shortCircuitBuffer.poll() match {
+      shortCircuitBuffer.pollFirst() match {
         case b: BoundaryEvent => processEvent(b)
         case Resume           => finishShellRegistration()
         case unexpected =>
@@ -845,7 +845,7 @@ import org.reactivestreams.Subscription
   override def postStop(): Unit = {
     if (shortCircuitBuffer ne null) {
       while (!shortCircuitBuffer.isEmpty) {
-        shortCircuitBuffer.poll() match {
+        shortCircuitBuffer.pollFirst() match {
           case b: BoundaryEvent =>
             // signal to telemetry that this event won't be processed
             b.cancel()