diff --git a/app/lib/activitypub/activity.rb b/app/lib/activitypub/activity.rb
index 224451f41..2b5d3ffc2 100644
--- a/app/lib/activitypub/activity.rb
+++ b/app/lib/activitypub/activity.rb
@@ -74,7 +74,7 @@ class ActivityPub::Activity
     @object_uri ||= begin
       str = value_or_id(@object)
 
-      if str.start_with?('bear:')
+      if str&.start_with?('bear:')
         Addressable::URI.parse(str).query_values['u']
       else
         str