diff --git a/lib/active_model_serializers.rb b/lib/active_model_serializers.rb
index e070f79f..6f0e89e7 100644
--- a/lib/active_model_serializers.rb
+++ b/lib/active_model_serializers.rb
@@ -7,6 +7,8 @@ if defined?(Rails)
   module ActiveModel
     class Railtie < Rails::Railtie
       generators do |app|
+        app ||= Rails.application # Rails 3.0.x does not yield `app`
+
         Rails::Generators.configure!(app.config.generators)
         require "generators/resource_override"
       end