diff --git a/akka-actor/src/main/scala/akka/event/EventBus.scala b/akka-actor/src/main/scala/akka/event/EventBus.scala
index 66b0aa0c29..cb83fbe806 100644
--- a/akka-actor/src/main/scala/akka/event/EventBus.scala
+++ b/akka-actor/src/main/scala/akka/event/EventBus.scala
@@ -143,7 +143,9 @@ trait SubchannelClassification { this: EventBus ⇒
 
   def unsubscribe(subscriber: Subscriber, from: Classifier): Boolean = subscriptions.synchronized {
     val diff = subscriptions.removeValue(from, subscriber)
-    cache ++= diff // FIXME What is the reason this isn't calling removeFromCache?
+    // removeValue(K, V) does not return the diff to remove from or add to the cache
+    // but instead the whole set of keys and values that should be updated in the cache
+    cache ++= diff
     diff.nonEmpty
   }
 
@@ -165,7 +167,6 @@ trait SubchannelClassification { this: EventBus ⇒
     recv foreach (publish(event, _))
   }
 
-  // we can only let keys that already exist in the cache get updated
   private def removeFromCache(changes: Seq[(Classifier, Set[Subscriber])]): Unit =
     cache = (cache /: changes) {
       case (m, (c, cs)) ⇒ m.updated(c, m.getOrElse(c, Set.empty[Subscriber]) -- cs)
diff --git a/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala b/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
index bff7a0ffee..ae82da6407 100644
--- a/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
+++ b/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
@@ -132,11 +132,14 @@ private[akka] class SubclassifiedIndex[K, V] private (private var values: Set[V]
   /**
    * Remove value from all keys which are subclasses of the given key.
    *
-   * @return the complete changes that should be inserted in the cache
+   * @return the complete changes that should be updated in the cache
    */
   def removeValue(key: K, value: V): Changes =
+    // the reason for not using the values in the returned diff is that we need to
+    // go through the whole tree to find all values for the "changed" keys in other
+    // parts of the tree as well, since new nodes might have been created
     mergeChangesByKey(innerRemoveValue(key, value)) map {
-      case (k, v) ⇒ (k, findValues(k))
+      case (k, _) ⇒ (k, findValues(k))
     }
 
   // this will return the keys and values to be removed from the cache