diff --git a/zephyr/static/js/zephyr.js b/zephyr/static/js/zephyr.js
index 805f2eed37..0a90e99d2b 100644
--- a/zephyr/static/js/zephyr.js
+++ b/zephyr/static/js/zephyr.js
@@ -479,7 +479,7 @@ function add_message_metadata(message, dummy) {
     $.each(involved_people, function (idx, person) {
         // Do the hasOwnProperty() call via the prototype to avoid problems
         // with keys like "hasOwnProperty"
-        if (! typeahead_helper.known_to_typeahead(person)) {
+        if (!typeahead_helper.known_to_typeahead(person) && people_dict[person.email] === undefined) {
             add_person(person);
             typeahead_helper.autocomplete_needs_update(true);
         }