Index: app/helpers/application_helper.rb
===================================================================
--- app/helpers/application_helper.rb	(revision 11981)
+++ app/helpers/application_helper.rb	(working copy)
@@ -1210,9 +1210,13 @@
   end
 
   def favicon
-    "<link rel='shortcut icon' href='#{image_path('/favicon.ico')}' />".html_safe
+    "<link rel='shortcut icon' href='#{favicon_path}' />".html_safe
   end
 
+  def favicon_path
+    image_path('/favicon.ico')
+  end
+
   def robot_exclusion_tag
     '<meta name="robots" content="noindex,follow,noarchive" />'.html_safe
   end
Index: app/views/common/feed.atom.builder
===================================================================
--- app/views/common/feed.atom.builder	(revision 11981)
+++ app/views/common/feed.atom.builder	(working copy)
@@ -3,7 +3,11 @@
   xml.title   truncate_single_line(@title, :length => 100)
   xml.link    "rel" => "self", "href" => url_for(params.merge(:only_path => false))
   xml.link    "rel" => "alternate", "href" => url_for(params.merge(:only_path => false, :format => nil, :key => nil))
-  xml.id      url_for(:controller => 'welcome', :only_path => false)
+
+  app_base_uri = url_for(:controller => 'welcome', :only_path => false, :trailing_slash => true)
+  xml.icon    app_base_uri + (favicon_path.start_with?('/') ? favicon_path[1..-1] : favicon_path)
+  xml.id      app_base_uri
+
   xml.updated((@items.first ? @items.first.event_datetime : Time.now).xmlschema)
   xml.author  { xml.name "#{Setting.app_title}" }
   xml.generator(:uri => Redmine::Info.url) { xml.text! Redmine::Info.app_name; }