diff --git a/static/js/message_list.js b/static/js/message_list.js
index 655526d642..2dabd09b05 100644
--- a/static/js/message_list.js
+++ b/static/js/message_list.js
@@ -55,7 +55,11 @@ exports.MessageList.prototype = {
                     return;
                 }
 
-                // Put messages in correct order on either side of the message list
+                // Put messages in correct order on either side of the
+                // message list.  This code path assumes that messages
+                // is a (1) sorted, and (2) consecutive block of
+                // messages that belong in this message list; those
+                // facts should be ensured by the caller.
                 if (self.empty() || msg.id > self.last().id) {
                     bottom_messages.push(msg);
                 } else if (msg.id < self.first().id) {
diff --git a/static/js/server_events.js b/static/js/server_events.js
index 9cd980cd92..358d4adb76 100644
--- a/static/js/server_events.js
+++ b/static/js/server_events.js
@@ -89,6 +89,10 @@ function get_events_success(events) {
     });
 
     if (messages.length !== 0) {
+        // Sort by ID, so that if we get multiple messages back from
+        // the server out-of-order, we'll still end up with our
+        // message lists in order.
+        messages = _.sortBy(messages, 'id');
         try {
             messages = echo.process_from_server(messages);
             message_events.insert_new_messages(messages);