diff --git a/django/db/models/manipulators.py b/django/db/models/manipulators.py
index d1ced1895a..06f31d8dc7 100644
--- a/django/db/models/manipulators.py
+++ b/django/db/models/manipulators.py
@@ -509,7 +509,7 @@ def manipulator_validator_unique_for_date(from_field, date_field, opts, lookup_t
     if lookup_type == 'date':
         lookup_kwargs['%s__day' % date_field.name] = date_val.day
     try:
-        old_obj = opts.model._default_manager.get_object(**lookup_kwargs)
+        old_obj = self.manager.get_object(**lookup_kwargs)
     except ObjectDoesNotExist:
         return
     else: