diff --git a/frontend_tests/node_tests/search_suggestion.js b/frontend_tests/node_tests/search_suggestion.js
index ada2ad3773..9a62031f8d 100644
--- a/frontend_tests/node_tests/search_suggestion.js
+++ b/frontend_tests/node_tests/search_suggestion.js
@@ -432,16 +432,29 @@ init();
         return 'office';
     };
 
-    global.stream_data.populate_stream_topics_for_tests({
-        devel: [
-            {subject: 'REXX'},
-        ],
-        office: [
-            {subject: 'team'},
-            {subject: 'ignore'},
-            {subject: 'test'},
-        ],
-    });
+    var devel_id = 44;
+    var office_id = 77;
+
+    global.stream_data.get_stream_id = function (stream_name) {
+        switch (stream_name) {
+            case 'office': return office_id;
+            case 'devel': return devel_id;
+        }
+    };
+
+    var recent_data = {};
+
+    recent_data[devel_id] = [
+        {subject: 'REXX'},
+    ];
+
+    recent_data[office_id] = [
+        {subject: 'team'},
+        {subject: 'ignore'},
+        {subject: 'test'},
+    ];
+
+    global.stream_data.populate_stream_topics_for_tests(recent_data);
 
     suggestions = search.get_suggestions('te');
     expected = [
diff --git a/frontend_tests/node_tests/stream_data.js b/frontend_tests/node_tests/stream_data.js
index bf24b6eb49..f7dc89f35e 100644
--- a/frontend_tests/node_tests/stream_data.js
+++ b/frontend_tests/node_tests/stream_data.js
@@ -240,8 +240,17 @@ var people = global.people;
 }());
 
 (function test_process_message_for_recent_topics() {
+    var stream_id = 55;
+
+    var rome = {
+        name: 'Rome',
+        stream_id: stream_id,
+    };
+
+    stream_data.add_sub('Rome', rome);
+
     var message = {
-        stream: 'Rome',
+        stream_id: stream_id,
         timestamp: 101,
         subject: 'toPic1',
     };
@@ -258,7 +267,7 @@ var people = global.people;
     ]);
 
     message = {
-        stream: 'Rome',
+        stream_id: stream_id,
         timestamp: 102,
         subject: 'Topic1',
     };
@@ -274,7 +283,7 @@ var people = global.people;
     ]);
 
     message = {
-        stream: 'Rome',
+        stream_id: stream_id,
         timestamp: 103,
         subject: 'topic2',
     };
@@ -321,13 +330,13 @@ var people = global.people;
     stream_data.unsubscribe_myself(sub);
     assert(!stream_data.is_active(sub));
 
-    sub = {name: 'lunch', subscribed: false, stream_id: 1};
+    sub = {name: 'lunch', subscribed: false, stream_id: 222};
     stream_data.add_sub('lunch', sub);
 
     assert(!stream_data.is_active(sub));
 
     var message = {
-        stream: 'lunch',
+        stream_id: 222,
         timestamp: 108,
         subject: 'topic2',
     };
diff --git a/frontend_tests/node_tests/topic_list.js b/frontend_tests/node_tests/topic_list.js
index 9963681ac4..fc4e2caadb 100644
--- a/frontend_tests/node_tests/topic_list.js
+++ b/frontend_tests/node_tests/topic_list.js
@@ -19,19 +19,21 @@ var topic_list = require('js/topic_list.js');
 global.compile_template('topic_list_item');
 
 (function test_topic_list_build_widget() {
+    var stream_id = 555;
     var stream = "devel";
     var active_topic = "testing";
     var max_topics = 5;
 
-    var topics = [
+    var recent_topics = {};
+    recent_topics[stream_id] = [
         {subject: "coding"},
     ];
-    global.stream_data.populate_stream_topics_for_tests({devel: topics});
+    global.stream_data.populate_stream_topics_for_tests(recent_topics);
     global.unread.num_unread_for_subject = function () {
         return 1;
     };
 
-    global.stream_data.get_stream_id = function () { return 99; };
+    global.stream_data.get_stream_id = function () { return stream_id; };
 
     var parent_elem = $('<div>');
     var widget = topic_list.build_widget(parent_elem, stream, active_topic, max_topics);
diff --git a/static/js/stream_data.js b/static/js/stream_data.js
index 2336198314..8c1cc170db 100644
--- a/static/js/stream_data.js
+++ b/static/js/stream_data.js
@@ -7,7 +7,7 @@ var exports = {};
 // Call clear_subscriptions() to initialize it.
 var stream_info;
 var subs_by_stream_id;
-var recent_topics = new Dict({fold_case: true});
+var recent_topics = new Dict(); // stream_id -> array of objects
 
 var stream_ids_by_name = new Dict({fold_case: true});
 
@@ -21,7 +21,7 @@ exports.clear_subscriptions = function () {
 exports.clear_subscriptions();
 
 exports.is_active = function (sub) {
-    return recent_topics.has(sub.name) || sub.newly_subscribed;
+    return recent_topics.has(sub.stream_id) || sub.newly_subscribed;
 };
 
 exports.rename_sub = function (sub, new_name) {
@@ -367,23 +367,19 @@ exports.process_message_for_recent_topics = function process_message_for_recent_
                                                 message, remove_message) {
     var current_timestamp = 0;
     var count = 0;
-    var stream = message.stream;
+    var stream_id = message.stream_id;
     var canon_subject = exports.canonicalized_name(message.subject);
 
-    if (! recent_topics.has(stream)) {
-        recent_topics.set(stream, []);
-    } else {
-        recent_topics.set(stream, _.filter(recent_topics.get(stream), function (item) {
-            var is_duplicate = (item.canon_subject.toLowerCase() === canon_subject.toLowerCase());
-            if (is_duplicate) {
-                current_timestamp = item.timestamp;
-                count = item.count;
-            }
-            return !is_duplicate;
-        }));
-    }
+    var recents = recent_topics.get(stream_id) || [];
 
-    var recents = recent_topics.get(stream);
+    recents = _.filter(recents, function (item) {
+        var is_duplicate = (item.canon_subject.toLowerCase() === canon_subject.toLowerCase());
+        if (is_duplicate) {
+            current_timestamp = item.timestamp;
+            count = item.count;
+        }
+        return !is_duplicate;
+    });
 
     if (remove_message !== undefined) {
         count = count - 1;
@@ -402,7 +398,7 @@ exports.process_message_for_recent_topics = function process_message_for_recent_
         return b.timestamp - a.timestamp;
     });
 
-    recent_topics.set(stream, recents);
+    recent_topics.set(stream_id, recents);
 };
 
 exports.get_streams_for_settings_page = function () {
@@ -451,12 +447,17 @@ exports.initialize_from_page_params = function () {
 };
 
 exports.get_recent_topics = function (stream_name) {
-    return recent_topics.get(stream_name);
+    var stream_id = exports.get_stream_id(stream_name);
+    if (!stream_id) {
+        return [];
+    }
+
+    return recent_topics.get(stream_id);
 };
 
 exports.populate_stream_topics_for_tests = function (stream_map) {
     // This is only used by tests.
-    recent_topics = Dict.from(stream_map, {fold_case: true});
+    recent_topics = Dict.from(stream_map);
 };
 
 exports.get_newbie_stream = function () {