1 files changed, 5 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
index d8146daa54..67e18d692d 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -7,7 +7,7 @@ module ActiveRecord
         else
           @target = (AssociationProxy === record ? record.target : record)
 
-          @owner[@reflection.primary_key_name] = record.id
+          @owner[@reflection.primary_key_name] = record_id(record)
           @owner[@reflection.options[:foreign_type]] = record.class.base_class.name.to_s
 
           @updated = true
@@ -41,6 +41,10 @@ module ActiveRecord
           !@owner[@reflection.primary_key_name].nil?
         end
 
+        def record_id(record)
+          record.send(@reflection.options[:primary_key] || :id)
+        end
+
         def association_class
           @owner[@reflection.options[:foreign_type]] ? @owner[@reflection.options[:foreign_type]].constantize : nil
         end