diff --git a/app/controllers/user_avatars_controller.rb b/app/controllers/user_avatars_controller.rb
index a44dd289c12..c2be05ce8d7 100644
--- a/app/controllers/user_avatars_controller.rb
+++ b/app/controllers/user_avatars_controller.rb
@@ -74,7 +74,7 @@ class UserAvatarsController < ApplicationController
         if optimized = get_optimized_image(upload, size)
           unless optimized.local?
             expires_in 1.day, public: true
-            return redirect_to optimized.url
+            return redirect_to Discourse.store.cdn_url(optimized.url)
           end
           image = Discourse.store.path_for(optimized)
         end
diff --git a/lib/file_store/base_store.rb b/lib/file_store/base_store.rb
index 74df43e1815..6fc9e688573 100644
--- a/lib/file_store/base_store.rb
+++ b/lib/file_store/base_store.rb
@@ -44,6 +44,10 @@ module FileStore
     def purge_tombstone(grace_period)
     end
 
+    def cdn_url(url)
+      url
+    end
+
   end
 
 end
diff --git a/lib/file_store/s3_store.rb b/lib/file_store/s3_store.rb
index 89e2deec803..4ee0da7f2bc 100644
--- a/lib/file_store/s3_store.rb
+++ b/lib/file_store/s3_store.rb
@@ -79,6 +79,14 @@ module FileStore
       end
     end
 
+    def cdn_url(url)
+      if SiteSetting.s3_cdn_url.present?
+        url.sub(absolute_base_url, SiteSetting.s3_cdn_url)
+      else
+        url
+      end
+    end
+
     private
 
       def get_path_for_upload(file, upload)
diff --git a/spec/controllers/user_avatars_controller_spec.rb b/spec/controllers/user_avatars_controller_spec.rb
index f25f0d3e46e..124580ee034 100644
--- a/spec/controllers/user_avatars_controller_spec.rb
+++ b/spec/controllers/user_avatars_controller_spec.rb
@@ -3,23 +3,34 @@ require 'spec_helper'
 describe UserAvatarsController do
 
   context 'show' do
-    it 'redirects to correct size for non local' do
+    it 'handles non local content correctly' do
       SiteSetting.avatar_sizes = "100|49"
       SiteSetting.enable_s3_uploads = true
       SiteSetting.s3_access_key_id = "XXX"
       SiteSetting.s3_secret_access_key = "XXX"
       SiteSetting.s3_upload_bucket = "test"
+      SiteSetting.s3_cdn_url = "http://cdn.com"
 
       GlobalSetting.expects(:cdn_url).returns("http://awesome.com/boom")
 
 
-      upload = Fabricate(:upload)
+      upload = Fabricate(:upload, url: "//test.s3-#{SiteSetting.s3_region}.amazonaws.com/something")
+      Fabricate(:optimized_image,
+                              sha1: SecureRandom.hex << "A"*8,
+                              upload: upload,
+                              width: 98,
+                              height: 98,
+                              url: "//test.s3-#{SiteSetting.s3_region}.amazonaws.com/something/else")
+
       user = Fabricate(:user, uploaded_avatar_id: upload.id)
 
       get :show, size: 97, username: user.username, version: upload.id, hostname: 'default'
 
       # 98 is closese which is 49 * 2 for retina
       expect(response).to redirect_to("http://awesome.com/boom/user_avatar/default/#{user.username_lower}/98/#{upload.id}.png")
+
+      get :show, size: 98, username: user.username, version: upload.id, hostname: 'default'
+      expect(response).to redirect_to("http://cdn.com/something/else")
     end
 
     it 'serves image even if size missing and its in local mode' do