diff --git a/railties/configs/initializers/new_rails_defaults.rb b/railties/configs/initializers/new_rails_defaults.rb
index 5e60c0ade4fe6..78e0117cc47e1 100644
--- a/railties/configs/initializers/new_rails_defaults.rb
+++ b/railties/configs/initializers/new_rails_defaults.rb
@@ -1,11 +1,13 @@
 # These settings change the behavior of Rails 2 apps and will be defaults
 # for Rails 3. You can remove this initializer when Rails 3 is released.
 
-# Include Active Record class name as root for JSON serialized output.
-ActiveRecord::Base.include_root_in_json = true
+if defined?(ActiveRecord)
+  # Include Active Record class name as root for JSON serialized output.
+  ActiveRecord::Base.include_root_in_json = true
 
-# Store the full class name (including module namespace) in STI type column.
-ActiveRecord::Base.store_full_sti_class = true
+  # Store the full class name (including module namespace) in STI type column.
+  ActiveRecord::Base.store_full_sti_class = true
+end
 
 # Use ISO 8601 format for JSON serialized times and dates.
 ActiveSupport.use_standard_json_time_format = true