diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index 97956ea3a1df4b92c2109bdcb25d06f0acd8c0aa..06b70c050eae5dbeed1d443a993110b9e0564686 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -106,10 +106,9 @@ def join_to(manager)
             end
 
             if reflection.type
-              scope_chain_items.concat [
+              scope_chain_items <<
                 ActiveRecord::Relation.new(reflection.klass, table)
                   .where(reflection.type => foreign_klass.base_class.name)
-              ]
             end
 
             scope_chain_items.concat [reflection.klass.send(:build_default_scope)].compact