diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index a56943d99d..7ecc5c19bd 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -1,6 +1,5 @@
require "active_support/core_ext/hash/keys"
require "active_support/core_ext/hash/reverse_merge"
-require "active_support/core_ext/hash/indifferent_access"
module ActiveSupport
# Implements a hash where keys :foo and "foo" are considered
@@ -41,6 +40,12 @@ module ActiveSupport
# rgb = { black: '#000000', white: '#FFFFFF' }.with_indifferent_access
#
# which may be handy.
+ #
+ # To access this class outside of Rails, require the core extension with:
+ #
+ # require "active_support/core_ext/hash/indifferent_access"
+ #
+ # which will, in turn, require this file.
class HashWithIndifferentAccess < Hash
# Returns +true+ so that Array#extract_options! finds members of
# this class.