diff --git a/akka-contrib/src/main/scala/akka/contrib/pattern/ClusterSharding.scala b/akka-contrib/src/main/scala/akka/contrib/pattern/ClusterSharding.scala
index 4347e01c3f..5e8a89734c 100644
--- a/akka-contrib/src/main/scala/akka/contrib/pattern/ClusterSharding.scala
+++ b/akka-contrib/src/main/scala/akka/contrib/pattern/ClusterSharding.scala
@@ -1098,21 +1098,29 @@ object ShardCoordinator {
 
       def updated(event: DomainEvent): State = event match {
         case ShardRegionRegistered(region) ⇒
+          require(!regions.contains(region), s"Region $region already registered: $this")
           copy(regions = regions.updated(region, Vector.empty))
         case ShardRegionProxyRegistered(proxy) ⇒
+          require(!regionProxies.contains(proxy), s"Region proxy $proxy already registered: $this")
           copy(regionProxies = regionProxies + proxy)
         case ShardRegionTerminated(region) ⇒
+          require(regions.contains(region), s"Terminated region $region not registered: $this")
           copy(
             regions = regions - region,
             shards = shards -- regions(region))
         case ShardRegionProxyTerminated(proxy) ⇒
+          require(regionProxies.contains(proxy), s"Terminated region proxy $proxy not registered: $this")
           copy(regionProxies = regionProxies - proxy)
         case ShardHomeAllocated(shard, region) ⇒
+          require(regions.contains(region), s"Region $region not registered: $this")
+          require(!shards.contains(shard), s"Shard [$shard] already allocated: $this")
           copy(
             shards = shards.updated(shard, region),
             regions = regions.updated(region, regions(region) :+ shard))
         case ShardHomeDeallocated(shard) ⇒
+          require(shards.contains(shard), s"Shard [$shard] not allocated: $this")
           val region = shards(shard)
+          require(regions.contains(region), s"Region $region for shard [$shard] not registered: $this")
           copy(
             shards = shards - shard,
             regions = regions.updated(region, regions(region).filterNot(_ == shard)))
@@ -1206,28 +1214,32 @@ class ShardCoordinator(handOffTimeout: FiniteDuration, rebalanceInterval: Finite
   }
 
   override def receiveRecover: Receive = {
-    case evt: DomainEvent ⇒ evt match {
-      case ShardRegionRegistered(region) ⇒
-        persistentState = persistentState.updated(evt)
-      case ShardRegionProxyRegistered(proxy) ⇒
-        persistentState = persistentState.updated(evt)
-      case ShardRegionTerminated(region) ⇒
-        if (persistentState.regions.contains(region))
+    case evt: DomainEvent ⇒
+      log.debug("receiveRecover {}", evt)
+      evt match {
+        case ShardRegionRegistered(region) ⇒
           persistentState = persistentState.updated(evt)
-        else {
-          log.debug("ShardRegionTerminated, but region {} was not registered. This inconsistency is due to that " +
-            " some stored ActorRef in Akka v2.3.0 and v2.3.1 did not contain full address information. It will be " +
-            "removed by later watch.", region)
-        }
-      case ShardRegionProxyTerminated(proxy) ⇒
-        persistentState = persistentState.updated(evt)
-      case _: ShardHomeAllocated ⇒
-        persistentState = persistentState.updated(evt)
-      case _: ShardHomeDeallocated ⇒
-        persistentState = persistentState.updated(evt)
-    }
+        case ShardRegionProxyRegistered(proxy) ⇒
+          persistentState = persistentState.updated(evt)
+        case ShardRegionTerminated(region) ⇒
+          if (persistentState.regions.contains(region))
+            persistentState = persistentState.updated(evt)
+          else {
+            log.debug("ShardRegionTerminated, but region {} was not registered. This inconsistency is due to that " +
+              " some stored ActorRef in Akka v2.3.0 and v2.3.1 did not contain full address information. It will be " +
+              "removed by later watch.", region)
+          }
+        case ShardRegionProxyTerminated(proxy) ⇒
+          if (persistentState.regionProxies.contains(proxy))
+            persistentState = persistentState.updated(evt)
+        case ShardHomeAllocated(shard, region) ⇒
+          persistentState = persistentState.updated(evt)
+        case _: ShardHomeDeallocated ⇒
+          persistentState = persistentState.updated(evt)
+      }
 
     case SnapshotOffer(_, state: State) ⇒
+      log.debug("receiveRecover SnapshotOffer {}", state)
       persistentState = state
   }
 
@@ -1274,6 +1286,8 @@ class ShardCoordinator(handOffTimeout: FiniteDuration, rebalanceInterval: Finite
           case None ⇒
             if (persistentState.regions.nonEmpty) {
               val region = allocationStrategy.allocateShard(sender(), shard, persistentState.regions)
+              require(persistentState.regions.contains(region),
+                s"Allocated region $region for shard [$shard] must be one of the registered regions: $persistentState")
               persist(ShardHomeAllocated(shard, region)) { evt ⇒
                 persistentState = persistentState.updated(evt)
                 log.debug("Shard [{}] allocated at [{}]", evt.shard, evt.region)
@@ -1296,10 +1310,12 @@ class ShardCoordinator(handOffTimeout: FiniteDuration, rebalanceInterval: Finite
     case RebalanceDone(shard, ok) ⇒
       rebalanceInProgress -= shard
       log.debug("Rebalance shard [{}] done [{}]", shard, ok)
-      if (ok) persist(ShardHomeDeallocated(shard)) { evt ⇒
-        persistentState = persistentState.updated(evt)
-        log.debug("Shard [{}] deallocated", evt.shard)
-      }
+      // The shard could have been removed by ShardRegionTerminated
+      if (ok && persistentState.shards.contains(shard))
+        persist(ShardHomeDeallocated(shard)) { evt ⇒
+          persistentState = persistentState.updated(evt)
+          log.debug("Shard [{}] deallocated", evt.shard)
+        }
 
     case SnapshotTick ⇒
       log.debug("Saving persistent snapshot")
diff --git a/akka-persistence/src/main/scala/akka/persistence/Eventsourced.scala b/akka-persistence/src/main/scala/akka/persistence/Eventsourced.scala
index 918121653d..9eeaf02a3b 100644
--- a/akka-persistence/src/main/scala/akka/persistence/Eventsourced.scala
+++ b/akka-persistence/src/main/scala/akka/persistence/Eventsourced.scala
@@ -369,6 +369,16 @@ private[persistence] trait Eventsourced extends ProcessorImpl {
     currentState.aroundReceive(receive, message)
   }
 
+  /**
+   * INTERNAL API.
+   */
+  override protected[akka] def aroundPreRestart(reason: Throwable, message: Option[Any]): Unit = {
+    // flushJournalBatch will send outstanding persistAsync and defer events to the journal
+    // and also prevent those to be unstashed in Processor.aroundPreRestart
+    flushJournalBatch()
+    super.aroundPreRestart(reason, message)
+  }
+
   /**
    * Calls `super.preRestart` then unstashes all messages from the internal stash.
    */
diff --git a/akka-persistence/src/main/scala/akka/persistence/Processor.scala b/akka-persistence/src/main/scala/akka/persistence/Processor.scala
index bd9390a67c..53c1512713 100644
--- a/akka-persistence/src/main/scala/akka/persistence/Processor.scala
+++ b/akka-persistence/src/main/scala/akka/persistence/Processor.scala
@@ -145,8 +145,7 @@ private[akka] trait ProcessorImpl extends Actor with Recovery {
       processorBatch.length >= extension.settings.journal.maxMessageBatchSize
 
     def journalBatch(): Unit = {
-      journal ! WriteMessages(processorBatch, self, instanceId)
-      processorBatch = Vector.empty
+      flushJournalBatch()
       batching = true
     }
   }
@@ -257,6 +256,14 @@ private[akka] trait ProcessorImpl extends Actor with Recovery {
     journal ! DeleteMessagesTo(persistenceId, toSequenceNr, permanent)
   }
 
+  /**
+   * INTERNAL API
+   */
+  private[akka] def flushJournalBatch(): Unit = {
+    journal ! WriteMessages(processorBatch, self, instanceId)
+    processorBatch = Vector.empty
+  }
+
   /**
    * INTERNAL API.
    */