diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 12e007292a648cb7afd3932d36697ae1dac76f55..287bea719c212ab4d65ce41cb1c3ebe5aa5054e8 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -1,4 +1,5 @@
 require "cases/helper"
+require "active_support/core_ext/hash/indifferent_access"
 require "active_support/hash_with_indifferent_access"
 
 class AttributeAssignmentTest < ActiveModel::TestCase