diff --git a/app/models/grader_configuration.rb b/app/models/grader_configuration.rb
--- a/app/models/grader_configuration.rb
+++ b/app/models/grader_configuration.rb
@@ -9,6 +9,7 @@
   TEST_REQUEST_EARLY_TIMEOUT_KEY = 'contest.test_request.early_timeout'
   MULTICONTESTS_KEY = 'system.multicontests'
   CONTEST_TIME_LIMIT_KEY = 'contest.time_limit'
+  MULTIPLE_IP_LOGIN_KEY = 'right.multiple_ip_login'
 
   cattr_accessor :config_cache
   cattr_accessor :task_grading_info_cache