diff --git a/app/assets/javascripts/discourse/models/category.js b/app/assets/javascripts/discourse/models/category.js
index d4e963a681..2dae55ed8e 100644
--- a/app/assets/javascripts/discourse/models/category.js
+++ b/app/assets/javascripts/discourse/models/category.js
@@ -195,7 +195,7 @@ Discourse.Category.reopenClass({
   },
 
   list: function() {
-    return Discourse.Site.currentProp('categories');
+    return Discourse.Site.currentProp('sortedCategories');
   },
 
   findSingleBySlug: function(slug) {
diff --git a/app/assets/javascripts/discourse/models/site.js b/app/assets/javascripts/discourse/models/site.js
index e7bbcc7213..52ae7ca8dc 100644
--- a/app/assets/javascripts/discourse/models/site.js
+++ b/app/assets/javascripts/discourse/models/site.js
@@ -22,6 +22,10 @@ Discourse.Site = Discourse.Model.extend({
     return postActionTypes.filterProperty('is_flag', true);
   }.property('post_action_types.@each'),
 
+  sortedCategories: Em.computed.sort('categories', function(a, b) {
+    return (b.get('topic_count') || 0) - (a.get('topic_count') || 0);
+  }),
+
   postActionTypeById: function(id) {
     return this.get("postActionByIdLookup.action" + id);
   },
diff --git a/test/javascripts/models/nav_item_test.js b/test/javascripts/models/nav_item_test.js
index 82647d67c1..e8a619ae91 100644
--- a/test/javascripts/models/nav_item_test.js
+++ b/test/javascripts/models/nav_item_test.js
@@ -1,12 +1,12 @@
 module("Discourse.NavItem", {
   setup: function() {
     this.site = Discourse.Site.current();
-    this.originalCategories = Discourse.Site.currentProp('categories') || [];
-    this.site.set('categories', this.originalCategories.concat( [Discourse.Category.create({name: '确实是这样', id: 343434})] ));
+    this.asianCategory = Discourse.Category.create({name: '确实是这样', id: 343434});
+    this.site.get('categories').addObject(this.asianCategory);
   },
 
   teardown: function() {
-    this.site.set('categories', this.originalCategories);
+    this.site.get('categories').removeObject(this.asianCategory);
   }
 });