diff --git a/app/models/user.rb b/app/models/user.rb
index b3622024e..0ac0dcb74 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -597,7 +597,7 @@ class AnonymousUser < User
 
   def validate_on_create
     # There should be only one AnonymousUser in the database
-    errors.add_to_base 'An anonymous user already exists.' if AnonymousUser.find(:first)
+    errors.add :base, 'An anonymous user already exists.' if AnonymousUser.find(:first)
   end
 
   def available_custom_fields