diff --git a/frontend_tests/node_tests/unread.js b/frontend_tests/node_tests/unread.js
index 84eb0b0bf4..766526ee14 100644
--- a/frontend_tests/node_tests/unread.js
+++ b/frontend_tests/node_tests/unread.js
@@ -38,6 +38,14 @@ global.current_msg_list = current_msg_list;
 var home_msg_list = {};
 global.home_msg_list = home_msg_list;
 
+var me = {
+    email: 'me@example.com',
+    user_id: 30,
+    full_name: 'Me Myself',
+};
+people.add(me);
+people.initialize_current_user(me.user_id);
+
 var zero_counts = {
     private_message_count: 0,
     home_unread_messages: 0,
@@ -276,12 +284,6 @@ var zero_counts = {
     var counts = unread.get_counts();
     assert.equal(counts.private_message_count, 0);
 
-    var message = {
-        id: 15,
-        type: 'private',
-        reply_to: 'anybody@example.com',
-    };
-
     var anybody = {
         email: 'anybody@example.com',
         user_id: 999,
@@ -289,6 +291,15 @@ var zero_counts = {
     };
     people.add_in_realm(anybody);
 
+    var message = {
+        id: 15,
+        type: 'private',
+        display_recipient: [
+            {user_id: anybody.user_id},
+            {id: me.user_id},
+        ],
+    };
+
     unread.process_loaded_messages([message]);
 
     counts = unread.get_counts();
@@ -320,7 +331,7 @@ var zero_counts = {
 
     var message = {
         id: 15,
-        reply_to: 'alice@example.com',
+        display_recipient: [{id: alice.user_id}],
         type: 'private',
     };
 
@@ -406,7 +417,7 @@ var zero_counts = {
     var message = {
         id: 9,
         type: 'private',
-        reply_to: 'unknown@zulip.com',
+        display_recipient: [{id: 9999}],
     };
 
     unread.process_read_message(message);
diff --git a/static/js/people.js b/static/js/people.js
index a53a576753..09fde26cdc 100644
--- a/static/js/people.js
+++ b/static/js/people.js
@@ -188,6 +188,16 @@ exports.get_recipients = function (user_ids_string) {
     return names.join(', ');
 };
 
+exports.pm_reply_user_string = function (message) {
+    var user_ids = people.pm_with_user_ids(message);
+
+    if (!user_ids) {
+        return;
+    }
+
+    return user_ids.join(',');
+};
+
 exports.pm_reply_to = function (message) {
     var user_ids = people.pm_with_user_ids(message);
 
diff --git a/static/js/unread.js b/static/js/unread.js
index becd0d839a..ccb7bb7a82 100644
--- a/static/js/unread.js
+++ b/static/js/unread.js
@@ -151,7 +151,7 @@ exports.process_loaded_messages = function (messages) {
         }
 
         if (message.type === 'private') {
-            var user_ids_string = people.emails_strings_to_user_ids_string(message.reply_to);
+            var user_ids_string = people.pm_reply_user_string(message);
             if (user_ids_string) {
                 unread_privates.setdefault(user_ids_string, new Dict());
                 unread_privates.get(user_ids_string).set(message.id, true);
@@ -175,7 +175,7 @@ exports.process_loaded_messages = function (messages) {
 exports.process_read_message = function (message) {
 
     if (message.type === 'private') {
-        var user_ids_string = people.emails_strings_to_user_ids_string(message.reply_to);
+        var user_ids_string = people.pm_reply_user_string(message);
         if (user_ids_string) {
             var dict = unread_privates.get(user_ids_string);
             if (dict) {