diff --git a/akka-actor/src/main/scala/akka/actor/Actor.scala b/akka-actor/src/main/scala/akka/actor/Actor.scala
index cf35d68c8c..8fc7df93e5 100644
--- a/akka-actor/src/main/scala/akka/actor/Actor.scala
+++ b/akka-actor/src/main/scala/akka/actor/Actor.scala
@@ -7,7 +7,6 @@ package akka.actor
 import akka.AkkaException
 import scala.reflect.BeanProperty
 import scala.util.control.NoStackTrace
-import scala.collection.immutable.Stack
 import java.util.regex.Pattern
 
 /**
diff --git a/akka-actor/src/main/scala/akka/actor/ActorSystem.scala b/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
index 721375adda..c874d75afc 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
@@ -13,7 +13,6 @@ import java.io.Closeable
 import akka.dispatch.Await.{ Awaitable, CanAwait }
 import akka.util._
 import akka.util.internal.{ HashedWheelTimer, ConcurrentIdentityHashMap }
-import collection.immutable.Stack
 import java.util.concurrent.{ ThreadFactory, CountDownLatch, TimeoutException, RejectedExecutionException }
 import java.util.concurrent.TimeUnit.MILLISECONDS
 
@@ -685,8 +684,8 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
 
   final class TerminationCallbacks extends Runnable with Awaitable[Unit] {
     private val lock = new ReentrantGuard
-    private var callbacks: Stack[Runnable] = _ //non-volatile since guarded by the lock
-    lock withGuard { callbacks = Stack.empty[Runnable] }
+    private var callbacks: List[Runnable] = _ //non-volatile since guarded by the lock
+    lock withGuard { callbacks = Nil }
 
     private val latch = new CountDownLatch(1)
 
@@ -695,17 +694,17 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
         case 0 ⇒ throw new RejectedExecutionException("Must be called prior to system shutdown.")
         case _ ⇒ lock withGuard {
           if (latch.getCount == 0) throw new RejectedExecutionException("Must be called prior to system shutdown.")
-          else callbacks = callbacks.push(callback)
+          else callbacks ::= callback
         }
       }
     }
 
     final def run(): Unit = lock withGuard {
-      @tailrec def runNext(c: Stack[Runnable]): Stack[Runnable] = c.headOption match {
-        case None ⇒ Stack.empty[Runnable]
-        case Some(callback) ⇒
-          try callback.run() catch { case e ⇒ log.error(e, "Failed to run termination callback, due to [{}]", e.getMessage) }
-          runNext(c.pop)
+      @tailrec def runNext(c: List[Runnable]): List[Runnable] = c match {
+        case Nil ⇒ Nil
+        case callback :: _ ⇒
+          try callback.run() catch { case NonFatal(e) ⇒ log.error(e, "Failed to run termination callback, due to [{}]", e.getMessage) }
+          runNext(c.tail)
       }
       try { callbacks = runNext(callbacks) } finally latch.countDown()
     }
diff --git a/akka-actor/src/main/scala/akka/actor/Props.scala b/akka-actor/src/main/scala/akka/actor/Props.scala
index fc01a5ba36..82d97f5465 100644
--- a/akka-actor/src/main/scala/akka/actor/Props.scala
+++ b/akka-actor/src/main/scala/akka/actor/Props.scala
@@ -6,7 +6,6 @@ package akka.actor
 
 import akka.dispatch._
 import akka.japi.Creator
-import collection.immutable.Stack
 import akka.routing._
 
 /**
diff --git a/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala b/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
index ed151b6b12..f8efe4e2e5 100644
--- a/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
+++ b/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
@@ -5,9 +5,7 @@
 package akka.testkit
 
 import akka.actor._
-import akka.util.Duration
 import java.util.concurrent.atomic.AtomicLong
-import scala.collection.immutable.Stack
 import akka.dispatch._
 import akka.pattern.ask