diff --git a/app/models/event.rb b/app/models/event.rb
index 7fadeea8e..13b4c891a 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -323,7 +323,7 @@ def self.citations_aggregations(doi)
     } 
   end
 
-  def self.advanced_aggregations
+  def self.advanced_aggregations(doi=nil)
     {
       unique_obj_count: { cardinality: { field: 'obj_id' }},
       unique_subj_count: { cardinality: { field: 'subj_id' }}