diff --git a/app/models/activity_pub.rb b/app/models/activity_pub.rb
index 3887d512..33cd4d45 100644
--- a/app/models/activity_pub.rb
+++ b/app/models/activity_pub.rb
@@ -18,7 +18,7 @@ class ActivityPub < ApplicationRecord
   belongs_to :site
   belongs_to :object, polymorphic: true
   belongs_to :actor
-  belongs_to :remote_flag, class_name: 'ActivityPub::RemoteFlag'
+  belongs_to :remote_flag, optional: true, class_name: 'ActivityPub::RemoteFlag'
   has_many :activities
 
   validates :site_id, presence: true