diff --git a/plugin.rb b/plugin.rb
index cf4ea328..6b65cf3e 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -56,7 +56,7 @@ module ::DiscourseAssign
 
   frequency_field = PendingAssignsReminder::REMINDERS_FREQUENCY
   register_editable_user_custom_field frequency_field
-  User.register_custom_field_type frequency_field, :integer
+  register_user_custom_field_type(frequency_field, :integer, max_length: 10)
   DiscoursePluginRegistry.serialized_current_user_fields << frequency_field
   add_to_serializer(:user, :reminders_frequency) { RemindAssignsFrequencySiteSettings.values }