diff --git a/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardCoordinator.scala b/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardCoordinator.scala
index 9c5d3ab46b..6f28ac7313 100644
--- a/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardCoordinator.scala
+++ b/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardCoordinator.scala
@@ -1268,8 +1268,13 @@ class PersistentShardCoordinator(
 
       case StateInitialized =>
         stateInitialized()
+        log.debug("{}: Coordinator initialization completed", typeName)
         context.become(active.orElse[Any, Unit](receiveSnapshotResult))
 
+      case Register(region) =>
+        // region will retry so ok to ignore
+        log.debug("{}: Ignoring registration from region [{}] while initializing", typeName, region)
+
     }: Receive).orElse[Any, Unit](receiveTerminated).orElse[Any, Unit](receiveSnapshotResult)
 
   def receiveSnapshotResult: Receive = {
diff --git a/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardRegion.scala b/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardRegion.scala
index 78f56b2fdc..c606069bb5 100644
--- a/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardRegion.scala
+++ b/akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardRegion.scala
@@ -231,9 +231,13 @@ object ShardRegion {
   @SerialVersionUID(1L) case object GetCurrentRegions extends ShardRegionQuery with ClusterShardingSerializable
 
   /**
-   * Java API:
+   * Java API: Send this message to the `ShardRegion` actor to request for [[CurrentRegions]],
+   * which contains the addresses of all registered regions.
+   *
+   * Intended for testing purpose to see when cluster sharding is "ready" or to monitor
+   * the state of the shard regions.
    */
-  def getCurrentRegionsInstance = GetCurrentRegions
+  def getCurrentRegionsInstance: GetCurrentRegions.type = GetCurrentRegions
 
   /**
    * Reply to `GetCurrentRegions`
diff --git a/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/PersistentShardingMigrationSpec.scala b/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/PersistentShardingMigrationSpec.scala
index cf133d3088..2f8e9fb82d 100644
--- a/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/PersistentShardingMigrationSpec.scala
+++ b/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/PersistentShardingMigrationSpec.scala
@@ -6,6 +6,7 @@ package akka.cluster.sharding
 import java.util.UUID
 
 import akka.actor.{ ActorRef, ActorSystem, Props }
+import akka.cluster.sharding.ShardRegion.CurrentRegions
 import akka.cluster.{ Cluster, MemberStatus }
 import akka.persistence.PersistentActor
 import akka.testkit.{ AkkaSpec, ImplicitSender, TestProbe }
@@ -106,10 +107,11 @@ class PersistentShardingMigrationSpec extends AkkaSpec(PersistentShardingMigrati
   import PersistentShardingMigrationSpec._
 
   "Migration" should {
-    "allow migration of remembered shards and now allow going back" in {
+    "allow migration of remembered shards and not allow going back" in {
       val typeName = "Migration"
 
       withSystem(config, typeName, "OldMode") { (_, region, _) =>
+        assertRegionRegistrationComplete(region)
         region ! Message(1)
         expectMsg("ack")
         region ! Message(2)
@@ -119,6 +121,7 @@ class PersistentShardingMigrationSpec extends AkkaSpec(PersistentShardingMigrati
       }
 
       withSystem(configForNewMode, typeName, "NewMode") { (system, region, rememberedEntitiesProbe) =>
+        assertRegionRegistrationComplete(region)
         val probe = TestProbe()(system)
         region.tell(Message(1), probe.ref)
         probe.expectMsg("ack")
@@ -172,5 +175,13 @@ class PersistentShardingMigrationSpec extends AkkaSpec(PersistentShardingMigrati
         Await.ready(system.terminate(), 20.seconds)
       }
     }
+
+    def assertRegionRegistrationComplete(region: ActorRef): Unit = {
+      awaitAssert {
+        region ! ShardRegion.GetCurrentRegions
+        expectMsgType[CurrentRegions].regions should have size (1)
+      }
+    }
   }
+
 }
diff --git a/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/RememberEntitiesShardIdExtractorChangeSpec.scala b/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/RememberEntitiesShardIdExtractorChangeSpec.scala
index f2cc684354..ee34ef0631 100644
--- a/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/RememberEntitiesShardIdExtractorChangeSpec.scala
+++ b/akka-cluster-sharding/src/test/scala/akka/cluster/sharding/RememberEntitiesShardIdExtractorChangeSpec.scala
@@ -10,6 +10,7 @@ import akka.actor.ActorRef
 import akka.actor.ActorSystem
 import akka.actor.Props
 import akka.cluster.Cluster
+import akka.cluster.sharding.ShardRegion.CurrentRegions
 import akka.persistence.PersistentActor
 import akka.testkit.AkkaSpec
 import akka.testkit.ImplicitSender
@@ -85,6 +86,7 @@ class RememberEntitiesShardIdExtractorChangeSpec
     "allow a change to the shard id extractor" in {
 
       withSystem("FirstShardIdExtractor", firstExtractShardId) { (_, region) =>
+        assertRegionRegistrationComplete(region)
         region ! Message(1)
         expectMsg("ack")
         region ! Message(11)
@@ -132,5 +134,13 @@ class RememberEntitiesShardIdExtractorChangeSpec
         Await.ready(system.terminate(), 20.seconds)
       }
     }
+
+    def assertRegionRegistrationComplete(region: ActorRef): Unit = {
+      awaitAssert {
+        region ! ShardRegion.GetCurrentRegions
+        expectMsgType[CurrentRegions].regions should have size (1)
+      }
+    }
   }
+
 }