diff --git a/frontend_tests/node_tests/dispatch.js b/frontend_tests/node_tests/dispatch.js
index 5abcbde681..65a1e65186 100644
--- a/frontend_tests/node_tests/dispatch.js
+++ b/frontend_tests/node_tests/dispatch.js
@@ -649,10 +649,10 @@ run(function (override, capture, args) {
     assert_same(args.sub, event.subscriptions[0]);
 
     event = event_fixtures.subscription__peer_add;
-    override('stream_data', 'add_subscriber', capture(['sub', 'email']));
+    override('stream_data', 'add_subscriber', capture(['sub', 'user_id']));
     dispatch(event);
     assert_same(args.sub, event.subscriptions[0]);
-    assert_same(args.email, 'bob@example.com');
+    assert_same(args.user_id, 555);
 
     event = event_fixtures.subscription__peer_remove;
     override('stream_data', 'remove_subscriber', capture(['sub', 'email']));
diff --git a/frontend_tests/node_tests/stream_data.js b/frontend_tests/node_tests/stream_data.js
index 43a53c88f1..15071bc36e 100644
--- a/frontend_tests/node_tests/stream_data.js
+++ b/frontend_tests/node_tests/stream_data.js
@@ -134,14 +134,14 @@ var people = global.people;
     assert(!stream_data.user_is_subscribed('Rome', email));
 
     // add
-    stream_data.add_subscriber('Rome', email);
+    stream_data.add_subscriber('Rome', brutus.user_id);
     assert(stream_data.user_is_subscribed('Rome', email));
     sub = stream_data.get_sub('Rome');
     stream_data.update_subscribers_count(sub);
     assert.equal(sub.subscriber_count, 1);
 
     // verify that adding an already-added subscriber is a noop
-    stream_data.add_subscriber('Rome', email);
+    stream_data.add_subscriber('Rome', brutus.user_id);
     assert(stream_data.user_is_subscribed('Rome', email));
     sub = stream_data.get_sub('Rome');
     stream_data.update_subscribers_count(sub);
@@ -165,14 +165,14 @@ var people = global.people;
     // can be undefined.
     stream_data.set_subscribers(sub);
     stream_data.add_sub('Rome', sub);
-    stream_data.add_subscriber('Rome', email);
+    stream_data.add_subscriber('Rome', brutus.user_id);
     sub.subscribed = true;
     assert(stream_data.user_is_subscribed('Rome', email));
 
-    // Verify that we noop and don't crash when unsubsribed.
+    // Verify that we noop and don't crash when unsubscribed.
     sub.subscribed = false;
     global.blueslip.warn = function () {};
-    stream_data.add_subscriber('Rome', email);
+    stream_data.add_subscriber('Rome', brutus.user_id);
     assert.equal(stream_data.user_is_subscribed('Rome', email), undefined);
     stream_data.remove_subscriber('Rome', email);
     assert.equal(stream_data.user_is_subscribed('Rome', email), undefined);
diff --git a/static/js/server_events.js b/static/js/server_events.js
index 8611884929..1d7444bda6 100644
--- a/static/js/server_events.js
+++ b/static/js/server_events.js
@@ -133,7 +133,7 @@ function dispatch_normal_event(event) {
             person = people.get_person_from_user_id(event.user_id);
             email = person.email;
             _.each(event.subscriptions, function (sub) {
-                stream_data.add_subscriber(sub, email);
+                stream_data.add_subscriber(sub, event.user_id);
                 $(document).trigger('peer_subscribe.zulip',
                                     {stream_name: sub, user_email: email});
             });
diff --git a/static/js/stream_data.js b/static/js/stream_data.js
index 39f2ce9a00..3d7e270ddc 100644
--- a/static/js/stream_data.js
+++ b/static/js/stream_data.js
@@ -146,15 +146,15 @@ exports.set_subscriber_emails = function (sub, emails) {
     });
 };
 
-exports.add_subscriber = function (stream_name, user_email) {
+exports.add_subscriber = function (stream_name, user_id) {
     var sub = exports.get_sub(stream_name);
     if (typeof sub === 'undefined') {
         blueslip.warn("We got an add_subscriber call for a non-existent stream.");
         return;
     }
-    var user_id = people.get_user_id(user_email);
-    if (!user_id) {
-        blueslip.error("We tried to add invalid subscriber: " + user_email);
+    var person = people.get_person_from_user_id(user_id);
+    if (person === undefined) {
+        blueslip.error("We tried to add invalid subscriber: " + user_id);
         return;
     }
     sub.subscribers.set(user_id, true);