diff --git a/src/org/jgroups/protocols/UNICAST3.java b/src/org/jgroups/protocols/UNICAST3.java
index df4d8e9a25..352897a00e 100644
--- a/src/org/jgroups/protocols/UNICAST3.java
+++ b/src/org/jgroups/protocols/UNICAST3.java
@@ -619,33 +619,35 @@ public Object down(Event evt) {
         switch (evt.getType()) {
 
             case Event.VIEW_CHANGE:  // remove connections to peers that are not members anymore !
-                View view=evt.getArg();
-                List<Address> new_members=view.getMembers();
-                Set<Address> non_members=new HashSet<>(send_table.keySet());
-                non_members.addAll(recv_table.keySet());
-                members=new_members;
-                new_members.forEach(non_members::remove);
-                if(cache != null)
-                    cache.removeAll(new_members);
-
-                if(!non_members.isEmpty()) {
-                    log.trace("%s: closing connections of non members %s", local_addr, non_members);
-                    // remove all non members, except those from remote sites: https://issues.redhat.com/browse/JGRP-2729
-                    non_members.stream().filter(this::isLocal).forEach(this::closeConnection);
-                }
-                if(!new_members.isEmpty()) {
-                    for(Address mbr: new_members) {
-                        Entry e=send_table.get(mbr);
-                        if(e != null && e.state() == State.CLOSING)
-                            e.state(State.OPEN);
-                        e=recv_table.get(mbr);
-                        if(e != null && e.state() == State.CLOSING)
-                            e.state(State.OPEN);
+                synchronized (this) {
+                    View view = evt.getArg();
+                    List<Address> new_members = view.getMembers();
+                    Set<Address> non_members = new HashSet<>(send_table.keySet());
+                    non_members.addAll(recv_table.keySet());
+                    members = new_members;
+                    new_members.forEach(non_members::remove);
+                    if (cache != null)
+                        cache.removeAll(new_members);
+
+                    if (!non_members.isEmpty()) {
+                        log.trace("%s: closing connections of non members %s", local_addr, non_members);
+                        // remove all non members, except those from remote sites: https://issues.redhat.com/browse/JGRP-2729
+                        non_members.stream().filter(this::isLocal).forEach(this::closeConnection);
+                    }
+                    if (!new_members.isEmpty()) {
+                        for (Address mbr : new_members) {
+                            Entry e = send_table.get(mbr);
+                            if (e != null && e.state() == State.CLOSING)
+                                e.state(State.OPEN);
+                            e = recv_table.get(mbr);
+                            if (e != null && e.state() == State.CLOSING)
+                                e.state(State.OPEN);
+                        }
                     }
+                    xmit_task_map.keySet().retainAll(new_members);
+                    last_sync_sent.removeExpiredElements();
+                    break;
                 }
-                xmit_task_map.keySet().retainAll(new_members);
-                last_sync_sent.removeExpiredElements();
-                break;
         }
 
         return down_prot.down(evt);          // Pass on to the layer below us
@@ -1328,7 +1330,7 @@ public int removeConnections(boolean remove_send_connections, boolean remove_rec
     }
 
     @ManagedOperation(description="Triggers the retransmission task")
-    public void triggerXmit() {
+    public synchronized void triggerXmit() {
         // check for gaps in the received messages and ask senders to send them again
         for(Map.Entry<Address,ReceiverEntry> entry: recv_table.entrySet()) {
             Address        target=entry.getKey(); // target to send retransmit requests to