Allow default scope to beconfigured.

lib/devise.rb

@@ -138,6 +138,9 @@ rescue
   require 'warden'
 end
 
+# Set the default_scope to nil, so it's overwritten when the first route is declared.
+Warden::Manager.default_scope = nil
+
 require 'devise/strategies/base'
 require 'devise/serializers/base'
 

lib/devise/rails/routes.rb

@@ -85,6 +85,7 @@ module ActionController::Routing
         resources.map!(&:to_sym)
         resources.each do |resource|
           mapping = Devise::Mapping.new(resource, options.dup)
+          Warden::Manager.default_scope ||= mapping.name
           Devise.mappings[mapping.name] = mapping
 
           route_options = mapping.route_options.merge(:path_prefix => mapping.raw_path, :name_prefix => "#{mapping.name}_")