diff --git a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
index fe8e871fed294..57f40f33bf5d9 100644
--- a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/numeric/inquiry'
+
 module ActiveSupport
   module NumberHelper
     class NumberToCurrencyConverter < NumberConverter # :nodoc: