diff --git a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
index e10175f346..08b362dce0 100644
--- a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
@@ -236,10 +236,28 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
   /**
    * Try to join this cluster node with the node specified by 'address'.
    * A 'Join(selfAddress)' command is sent to the node to join.
+   *
+   * An actor system can only join a cluster once. Additional attempts will be ignored.
+   * When it has successfully joined it must be restarted to be able to join another
+   * cluster or to join the same cluster again.
    */
   def join(address: Address): Unit =
     clusterCore ! ClusterUserAction.JoinTo(address)
 
+  /**
+   * Join the specified seed nodes without defining them in config.
+   * Especially useful from tests when Addresses are unknown before startup time.
+   *
+   * An actor system can only join a cluster once. Additional attempts will be ignored.
+   * When it has successfully joined it must be restarted to be able to join another
+   * cluster or to join the same cluster again.
+   *
+   * JAVA API: Use akka.japi.Util.immutableSeq to convert a java.lang.Iterable
+   * to the type needed for the seedNodes parameter.
+   */
+  def joinSeedNodes(seedNodes: immutable.Seq[Address]): Unit =
+    clusterCore ! InternalClusterAction.JoinSeedNodes(seedNodes.toVector)
+
   /**
    * Send command to issue state transition to LEAVING for the node specified by 'address'.
    */
@@ -273,14 +291,6 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
   // ===================== INTERNAL API =====================
   // ========================================================
 
-  /**
-   * Make it possible to join the specified seed nodes without defining them
-   * in config. Especially useful from tests when Addresses are unknown
-   * before startup time.
-   */
-  private[cluster] def joinSeedNodes(seedNodes: immutable.IndexedSeq[Address]): Unit =
-    clusterCore ! InternalClusterAction.JoinSeedNodes(seedNodes)
-
   /**
    * INTERNAL API.
    *
diff --git a/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala b/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
index ded59ec978..79c8be0ba4 100644
--- a/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
@@ -327,7 +327,9 @@ private[cluster] class ClusterCoreDaemon(publisher: ActorRef) extends Actor with
     case msg: SubscriptionMessage         ⇒ publisher forward msg
     case ClusterUserAction.JoinTo(address) ⇒
       logInfo("Trying to join [{}] when already part of a cluster, ignoring", address)
-
+    case JoinSeedNodes(seedNodes) ⇒
+      logInfo("Trying to join seed nodes [{}] when already part of a cluster, ignoring",
+        seedNodes.mkString(", "))
   }
 
   def removed: Actor.Receive = {