diff --git a/static/js/composebox_typeahead.js b/static/js/composebox_typeahead.js
index 0509d654f9..72527ea39a 100644
--- a/static/js/composebox_typeahead.js
+++ b/static/js/composebox_typeahead.js
@@ -28,6 +28,32 @@ exports.get_cleaned_pm_recipients = function (query_string) {
     return recipients;
 };
 
+function case_insensitive_find(term, array) {
+    var lowered_term = term.toLowerCase();
+    return _.filter(array, function (elt) {
+        return elt.toLowerCase() === lowered_term;
+    }).length !== 0;
+}
+
+var seen_topics = new Dict();
+
+exports.add_topic = function (stream, topic) {
+    if (! seen_topics.has(stream)) {
+        seen_topics.set(stream, []);
+    }
+    if (! case_insensitive_find(topic, seen_topics.get(stream))) {
+        seen_topics.get(stream).push(topic);
+        seen_topics.get(stream).sort();
+    }
+};
+
+exports.topics_seen_for = function (stream) {
+    if (seen_topics.has(stream)) {
+        return seen_topics.get(stream);
+    }
+    return [];
+};
+
 function get_last_recipient_in_pm(query_string) {
     var recipients = get_pm_recipients(query_string);
     return recipients[recipients.length-1];
@@ -202,11 +228,8 @@ exports.initialize = function () {
 
     $( "#subject" ).typeahead({
         source: function (query, process) {
-            var stream_name = $("#stream").val(), i;
-            if (subject_dict.has(stream_name)) {
-                return subject_dict.get(stream_name);
-            }
-            return [];
+            var stream_name = $("#stream").val();
+            return exports.topics_seen_for(stream_name);
         },
         items: 3,
         highlighter: composebox_typeahead_highlighter,
diff --git a/static/js/zulip.js b/static/js/zulip.js
index 23b384225e..8856e32c31 100644
--- a/static/js/zulip.js
+++ b/static/js/zulip.js
@@ -5,7 +5,6 @@ var home_msg_list = new MessageList('zhome',
 );
 var narrowed_msg_list;
 var current_msg_list = home_msg_list;
-var subject_dict = new Dict();
 var people_dict = new Dict();
 var recent_subjects = new Dict();
 
@@ -474,13 +473,6 @@ function unconditionally_send_pointer_update() {
     }
 }
 
-function case_insensitive_find(term, array) {
-    var lowered_term = term.toLowerCase();
-    return _.filter(array, function (elt) {
-        return elt.toLowerCase() === lowered_term;
-    }).length !== 0;
-}
-
 function process_message_for_recent_subjects(message, remove_message) {
     var current_timestamp = 0;
     var count = 0;
@@ -554,13 +546,7 @@ function add_message_metadata(message) {
     case 'stream':
         message.is_stream = true;
         message.stream = message.display_recipient;
-        if (! subject_dict.has(message.stream)) {
-            subject_dict.set(message.stream, []);
-        }
-        if (! case_insensitive_find(message.subject, subject_dict.get(message.stream))) {
-            subject_dict.get(message.stream).push(message.subject);
-            subject_dict.get(message.stream).sort();
-        }
+        composebox_typeahead.add_topic(message.stream, message.subject);
         message.reply_to = message.sender_email;
 
         process_message_for_recent_subjects(message);
diff --git a/tools/jslint/check-all.js b/tools/jslint/check-all.js
index aed5035eeb..ccd331d3f7 100644
--- a/tools/jslint/check-all.js
+++ b/tools/jslint/check-all.js
@@ -40,7 +40,7 @@ var globals =
     // zulip.js
     + ' all_msg_list home_msg_list narrowed_msg_list current_msg_list get_updates_params'
     + ' add_messages'
-    + ' subject_dict people_dict'
+    + ' people_dict'
     + ' keep_pointer_in_view'
     + ' respond_to_message recenter_view last_viewport_movement_direction'
     + ' scroll_to_selected get_private_message_recipient'