diff --git a/clientsession.go b/clientsession.go
index a10e262..1b67ab1 100644
--- a/clientsession.go
+++ b/clientsession.go
@@ -86,6 +86,9 @@ type ClientSession struct {
 	hasPendingParticipantsUpdate bool
 
 	virtualSessions map[*VirtualSession]bool
+
+	seenJoinedLock   sync.Mutex
+	seenJoinedEvents map[string]bool
 }
 
 func NewClientSession(hub *Hub, privateId string, publicId string, data *SessionIdData, backend *Backend, hello *HelloClientMessage, auth *BackendClientAuthResponse) (*ClientSession, error) {
@@ -335,6 +338,10 @@ func (s *ClientSession) SetRoom(room *Room) {
 	} else {
 		atomic.StoreInt64(&s.roomJoinTime, 0)
 	}
+
+	s.seenJoinedLock.Lock()
+	defer s.seenJoinedLock.Unlock()
+	s.seenJoinedEvents = nil
 }
 
 func (s *ClientSession) GetRoom() *Room {
@@ -1153,6 +1160,29 @@ func filterDisplayNames(events []*EventServerMessageSessionEntry) []*EventServer
 	return result
 }
 
+func (s *ClientSession) filterDuplicateJoin(entries []*EventServerMessageSessionEntry) []*EventServerMessageSessionEntry {
+	s.seenJoinedLock.Lock()
+	defer s.seenJoinedLock.Unlock()
+
+	// Due to the asynchronous events, a session might received a "Joined" event
+	// for the same (other) session twice, so filter these out on a per-session
+	// level.
+	result := make([]*EventServerMessageSessionEntry, 0, len(entries))
+	for _, e := range entries {
+		if s.seenJoinedEvents[e.SessionId] {
+			log.Printf("Session %s got duplicate joined event for %s, ignoring", s.publicId, e.SessionId)
+			continue
+		}
+
+		if s.seenJoinedEvents == nil {
+			s.seenJoinedEvents = make(map[string]bool)
+		}
+		s.seenJoinedEvents[e.SessionId] = true
+		result = append(result, e)
+	}
+	return result
+}
+
 func (s *ClientSession) filterMessage(message *ServerMessage) *ServerMessage {
 	switch message.Type {
 	case "event":
@@ -1177,18 +1207,47 @@ func (s *ClientSession) filterMessage(message *ServerMessage) *ServerMessage {
 		case "room":
 			switch message.Event.Type {
 			case "join":
-				if s.HasPermission(PERMISSION_HIDE_DISPLAYNAMES) {
+				join := s.filterDuplicateJoin(message.Event.Join)
+				if len(join) == 0 {
+					return nil
+				}
+				copied := false
+				if len(join) != len(message.Event.Join) {
 					// Create unique copy of message for only this client.
+					copied = true
 					message = &ServerMessage{
 						Id:   message.Id,
 						Type: message.Type,
 						Event: &EventServerMessage{
 							Type:   message.Event.Type,
 							Target: message.Event.Target,
-							Join:   filterDisplayNames(message.Event.Join),
+							Join:   join,
 						},
 					}
 				}
+
+				if s.HasPermission(PERMISSION_HIDE_DISPLAYNAMES) {
+					if copied {
+						message.Event.Join = filterDisplayNames(message.Event.Join)
+					} else {
+						message = &ServerMessage{
+							Id:   message.Id,
+							Type: message.Type,
+							Event: &EventServerMessage{
+								Type:   message.Event.Type,
+								Target: message.Event.Target,
+								Join:   filterDisplayNames(message.Event.Join),
+							},
+						}
+					}
+				}
+			case "leave":
+				s.seenJoinedLock.Lock()
+				defer s.seenJoinedLock.Unlock()
+
+				for _, e := range message.Event.Leave {
+					delete(s.seenJoinedEvents, e)
+				}
 			case "message":
 				if message.Event.Message == nil || message.Event.Message.Data == nil || len(*message.Event.Message.Data) == 0 || !s.HasPermission(PERMISSION_HIDE_DISPLAYNAMES) {
 					return message
@@ -1265,7 +1324,7 @@ func (s *ClientSession) filterAsyncMessage(msg *AsyncMessage) *ServerMessage {
 				// Can happen mostly during tests where an older room async message
 				// could be received by a subscriber that joined after it was sent.
 				if joined := s.getRoomJoinTime(); joined.IsZero() || msg.SendTime.Before(joined) {
-					log.Printf("Message %+v was sent before room was joined, ignoring", msg.Message)
+					log.Printf("Message %+v was sent on %s before room was joined on %s, ignoring", msg.Message, msg.SendTime, joined)
 					return nil
 				}
 			}
diff --git a/hub_test.go b/hub_test.go
index 6d70cc1..12d0ec1 100644
--- a/hub_test.go
+++ b/hub_test.go
@@ -2401,51 +2401,12 @@ func TestClientMessageToUserIdMultipleSessions(t *testing.T) {
 func WaitForUsersJoined(ctx context.Context, t *testing.T, client1 *TestClient, hello1 *ServerMessage, client2 *TestClient, hello2 *ServerMessage) {
 	// We will receive "joined" events for all clients. The ordering is not
 	// defined as messages are processed and sent by asynchronous event handlers.
-	msg1_1, err := client1.RunUntilMessage(ctx)
-	if err != nil {
+	if err := client1.RunUntilJoined(ctx, hello1.Hello, hello2.Hello); err != nil {
 		t.Error(err)
 	}
-	msg1_2, err := client1.RunUntilMessage(ctx)
-	if err != nil {
+	if err := client2.RunUntilJoined(ctx, hello1.Hello, hello2.Hello); err != nil {
 		t.Error(err)
 	}
-	msg2_1, err := client2.RunUntilMessage(ctx)
-	if err != nil {
-		t.Error(err)
-	}
-	msg2_2, err := client2.RunUntilMessage(ctx)
-	if err != nil {
-		t.Error(err)
-	}
-
-	if err := client1.checkMessageJoined(msg1_1, hello1.Hello); err != nil {
-		// Ordering is "joined" from client 2, then from client 1
-		if err := client1.checkMessageJoined(msg1_1, hello2.Hello); err != nil {
-			t.Error(err)
-		}
-		if err := client1.checkMessageJoined(msg1_2, hello1.Hello); err != nil {
-			t.Error(err)
-		}
-	} else {
-		// Ordering is "joined" from client 1, then from client 2
-		if err := client1.checkMessageJoined(msg1_2, hello2.Hello); err != nil {
-			t.Error(err)
-		}
-	}
-	if err := client2.checkMessageJoined(msg2_1, hello1.Hello); err != nil {
-		// Ordering is "joined" from client 2, then from client 1
-		if err := client2.checkMessageJoined(msg2_1, hello2.Hello); err != nil {
-			t.Error(err)
-		}
-		if err := client2.checkMessageJoined(msg2_2, hello1.Hello); err != nil {
-			t.Error(err)
-		}
-	} else {
-		// Ordering is "joined" from client 1, then from client 2
-		if err := client2.checkMessageJoined(msg2_2, hello2.Hello); err != nil {
-			t.Error(err)
-		}
-	}
 }
 
 func TestClientMessageToRoom(t *testing.T) {
diff --git a/testclient_test.go b/testclient_test.go
index 86560c0..2f2fde7 100644
--- a/testclient_test.go
+++ b/testclient_test.go
@@ -770,7 +770,7 @@ func (c *TestClient) RunUntilJoinedAndReturn(ctx context.Context, hello ...*Hell
 	for len(hellos) > 0 {
 		message, err := c.RunUntilMessage(ctx)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, fmt.Errorf("got error while waiting for %+v: %w", hellos, err)
 		}
 
 		if err := checkMessageType(message, "event"); err != nil {