diff --git a/web/src/people.js b/web/src/people.js
index 6d0889f406..7d77e52d28 100644
--- a/web/src/people.js
+++ b/web/src/people.js
@@ -1269,7 +1269,13 @@ export function deactivate(person) {
 }
 
 export function report_late_add(user_id, email) {
-    if (reload_state.is_in_progress()) {
+    // If the events system is not running, then it is expected that
+    // we will fetch messages from the server that were sent by users
+    // who don't exist in our users data set. This can happen because
+    // we're in the middle of a reload (and thus stopped our event
+    // queue polling) or because we are a spectator and never had an
+    // event queue in the first place.
+    if (reload_state.is_in_progress() || page_params.is_spectator) {
         blueslip.log("Added user late", {user_id, email});
     } else {
         blueslip.error("Added user late", {user_id, email});
diff --git a/web/src/server_events.js b/web/src/server_events.js
index bfbb59523c..f7cbb08837 100644
--- a/web/src/server_events.js
+++ b/web/src/server_events.js
@@ -154,8 +154,8 @@ function get_events({dont_block = false} = {}) {
     }
 
     // TODO: In the future, we may implement Tornado support for live
-    // update for spectator, but until then, there's nothing
-    // to do here.
+    // update for spectators (#20315), but until then, there's nothing
+    // to do here. Update report_late_add if this changes.
     if (page_params.is_spectator) {
         return;
     }