diff --git a/app/models/user_history.rb b/app/models/user_history.rb
index 9f0291fc91d..a68c1a0233b 100644
--- a/app/models/user_history.rb
+++ b/app/models/user_history.rb
@@ -5,7 +5,6 @@ class UserHistory < ActiveRecord::Base
   belongs_to :acting_user, class_name: 'User'
   belongs_to :target_user, class_name: 'User'
 
-  validates_presence_of :acting_user_id
   validates_presence_of :action
 
   scope :only_staff_actions, ->{ where("action IN (?)", UserHistory.staff_action_ids) }
@@ -15,7 +14,9 @@ class UserHistory < ActiveRecord::Base
                            :change_trust_level,
                            :change_site_setting,
                            :change_site_customization,
-                           :delete_site_customization)
+                           :delete_site_customization,
+                           :checked_for_custom_avatar,
+                           :notified_about_avatar)
   end
 
   # Staff actions is a subset of all actions, used to audit actions taken by staff users.
diff --git a/db/migrate/20130912185218_acting_user_null.rb b/db/migrate/20130912185218_acting_user_null.rb
new file mode 100644
index 00000000000..fe99e3783cc
--- /dev/null
+++ b/db/migrate/20130912185218_acting_user_null.rb
@@ -0,0 +1,10 @@
+class ActingUserNull < ActiveRecord::Migration
+  def up
+    change_column :user_histories, :acting_user_id, :integer, :null => true
+  end
+
+  def down
+    execute "DELETE FROM user_histories WHERE acting_user_id IS NULL"
+    change_column :user_histories, :acting_user_id, :integer, :null => false
+  end
+end
diff --git a/lib/jobs/detect_avatars.rb b/lib/jobs/detect_avatars.rb
index 25987ac8794..1c2c6ce004b 100644
--- a/lib/jobs/detect_avatars.rb
+++ b/lib/jobs/detect_avatars.rb
@@ -17,6 +17,10 @@ module Jobs
       if user_stats.present?
         user_stats.each do |us|
           us.update_column(:has_custom_avatar, true) if AvatarDetector.new(us.user).has_custom_avatar?
+          UserHistory.create!(
+            action: UserHistory.actions[:checked_for_custom_avatar],
+            target_user_id: us.user_id
+          )
         end
       end
     end