diff --git a/lib/naver/ext/hash/to_underscore_keys.rb b/lib/naver/ext/hash/to_underscore_keys.rb
index <HASH>..<HASH> 100644
--- a/lib/naver/ext/hash/to_underscore_keys.rb
+++ b/lib/naver/ext/hash/to_underscore_keys.rb
@@ -29,7 +29,7 @@ class Hash
   end
 
   def underscore(camel_cased_word)
-    return camel_cased_word unless /[A-Z-]|::/.match?(camel_cased_word)
+    return camel_cased_word unless camel_cased_word =~ /[A-Z-]|::/
     word = camel_cased_word.to_s.gsub("::".freeze, "/".freeze)
     word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
     word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
REGEX.match? is ruby <I> only. replace to =~