diff --git a/lib/devise/test/controller_helpers.rb b/lib/devise/test/controller_helpers.rb
index 198144ae..cd1a8be8 100644
--- a/lib/devise/test/controller_helpers.rb
+++ b/lib/devise/test/controller_helpers.rb
@@ -139,7 +139,7 @@ module Devise
 
           status, headers, response = Devise.warden_config[:failure_app].call(env).to_a
           @controller.response.headers.merge!(headers)
-          @controller.response.content_type = headers["Content-Type"] unless Rails.version.start_with?('5')
+          @controller.response.content_type = headers["Content-Type"] unless Rails::VERSION::MAJOR >= 5
           @controller.status = status
           @controller.response.body = response.body
           nil # causes process return @response