diff --git a/lib/pg_ldap_sync/application.rb b/lib/pg_ldap_sync/application.rb
index 539fe66..909167f 100644
--- a/lib/pg_ldap_sync/application.rb
+++ b/lib/pg_ldap_sync/application.rb
@@ -475,6 +475,7 @@ class Application
   def self.run(argv)
     s = self.new
     s.config_fname = '/etc/pg_ldap_sync.yaml'
+    s.groups_fname = ''
     s.log = Logger.new($stdout)
     s.log.level = Logger::ERROR