diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index bfb321f930..246f0761b3 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -226,7 +226,7 @@ def type
       end
 
       def primary_key_column
-        @primary_key_column ||= klass.columns.find { |c| c.name == klass.primary_key }
+        klass.columns_hash[klass.primary_key]
       end
 
       def association_foreign_key