diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index 16b28dd295..2ba56bc3c5 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -5,6 +5,7 @@ require 'active_support'
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/object/metaclass'
 require 'active_support/core_ext/array/extract_options'
+require 'active_support/core_ext/hash/deep_merge'
 require 'active_support/core_ext/module/attribute_accessors'
 require 'active_support/core_ext/string/inflections'
 
@@ -94,7 +95,7 @@ module Rails
     end
 
     def self.plugins_generators_paths #:nodoc:
-      return [] unless defined?(Rails.root)
+      return [] unless defined?(Rails.root) && Rails.root
       Dir[File.join(Rails.root, "vendor", "plugins", "*", "lib", "{generators,rails_generators}")]
     end
 
@@ -135,7 +136,7 @@ module Rails
     def self.load_paths
       @load_paths ||= begin
         paths = []
-        paths += Dir[File.join(Rails.root, "lib", "{generators,rails_generators}")] if defined?(Rails.root)
+        paths += Dir[File.join(Rails.root, "lib", "{generators,rails_generators}")] if defined?(Rails.root) && Rails.root
         paths += Dir[File.join(Thor::Util.user_home, ".rails", "{generators,rails_generators}")]
         paths += self.plugins_generators_paths
         paths += self.gems_generators_paths