1 files changed, 3 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/number_helper/number_to_phone_converter.rb b/activesupport/lib/active_support/number_helper/number_to_phone_converter.rb
index 1de9f50f34..96410f4995 100644
--- a/activesupport/lib/active_support/number_helper/number_to_phone_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_phone_converter.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 module ActiveSupport
   module NumberHelper
     class NumberToPhoneConverter < NumberConverter #:nodoc:
       def convert
-        str = country_code(opts[:country_code])
+        str = country_code(opts[:country_code]).dup
         str << convert_to_phone_number(number.to_s.strip)
         str << phone_ext(opts[:extension])
       end