diff --git a/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala b/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
index 77fecff161..b23c0f2108 100644
--- a/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala
@@ -301,7 +301,7 @@ private[cluster] final class ClusterCoreDaemon(environment: ClusterEnvironment)
 
       // add joining node as Joining
       // add self in case someone else joins before self has joined (Set discards duplicates)
-      val newMembers = localMembers :+ Member(node, Joining) :+ Member(selfAddress, Joining)
+      val newMembers = localMembers + Member(node, Joining) + Member(selfAddress, Joining)
       val newGossip = localGossip copy (overview = newOverview, members = newMembers)
 
       val versionedGossip = newGossip :+ vclockNode
diff --git a/akka-cluster/src/main/scala/akka/cluster/Gossip.scala b/akka-cluster/src/main/scala/akka/cluster/Gossip.scala
index 4d4685688f..643d0fd6fd 100644
--- a/akka-cluster/src/main/scala/akka/cluster/Gossip.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/Gossip.scala
@@ -84,7 +84,7 @@ case class Gossip(
    */
   def :+(member: Member): Gossip = {
     if (members contains member) this
-    else this copy (members = members :+ member)
+    else this copy (members = members + member)
   }
 
   /**
@@ -113,7 +113,7 @@ case class Gossip(
 
     // 4. merge members by selecting the single Member with highest MemberStatus out of the Member groups,
     //    and exclude unreachable
-    val mergedMembers = Gossip.emptyMembers :++ Member.pickHighestPriority(this.members, that.members).filterNot(mergedUnreachable.contains)
+    val mergedMembers = Gossip.emptyMembers ++ Member.pickHighestPriority(this.members, that.members).filterNot(mergedUnreachable.contains)
 
     // 5. fresh seen table
     val mergedSeen = Map.empty[Address, VectorClock]
diff --git a/akka-cluster/src/main/scala/akka/cluster/Member.scala b/akka-cluster/src/main/scala/akka/cluster/Member.scala
index d50131c85d..c7909b1834 100644
--- a/akka-cluster/src/main/scala/akka/cluster/Member.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/Member.scala
@@ -83,19 +83,6 @@ object Member {
     case (Up, Up)           ⇒ m1
   }
 
-  // FIXME Workaround for https://issues.scala-lang.org/browse/SI-5986
-  // SortedSet + and ++ operators replaces existing element
-  // Use these :+ and :++ operators for the Gossip members
-  implicit def sortedSetWorkaround(sortedSet: SortedSet[Member]): SortedSetWorkaround = new SortedSetWorkaround(sortedSet)
-  class SortedSetWorkaround(sortedSet: SortedSet[Member]) {
-    implicit def :+(elem: Member): SortedSet[Member] = {
-      if (sortedSet.contains(elem)) sortedSet
-      else sortedSet + elem
-    }
-
-    implicit def :++(elems: GenTraversableOnce[Member]): SortedSet[Member] =
-      sortedSet ++ (elems.toSet diff sortedSet)
-  }
 }
 
 /**