diff --git a/actionpack/lib/action_view/helpers/asset_tag_helper.rb b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
index 83357dd76f64730ed7c3ef49f1b0bce3a2f8063c..4df99f8293bce65e0f022ec77945c511eacdaaeb 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
@@ -140,7 +140,7 @@ module AssetTagHelper
         :stylesheets_dir => "#{assets_dir}/stylesheets",
       }
 
-      JAVASCRIPT_DEFAULT_SOURCES = ['prototype', 'effects', 'dragdrop', 'controls'].freeze unless const_defined?(:JAVASCRIPT_DEFAULT_SOURCES)
+      JAVASCRIPT_DEFAULT_SOURCES = ['prototype', 'effects', 'dragdrop', 'controls', 'rails'].freeze unless const_defined?(:JAVASCRIPT_DEFAULT_SOURCES)
 
       # Returns a link tag that browsers and news readers can use to auto-detect
       # an RSS or ATOM feed. The +type+ can either be <tt>:rss</tt> (default) or