diff --git a/lib/mcp/string_utils.rb b/lib/mcp/string_utils.rb
index 07e153e..2dd4e0f 100644
--- a/lib/mcp/string_utils.rb
+++ b/lib/mcp/string_utils.rb
@@ -15,7 +15,7 @@ def demodulize(path)
     end
 
     def underscore(camel_cased_word)
-      camel_cased_word.dup
+      camel_cased_word
         .gsub(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
         .gsub(/([a-z\d])([A-Z])/, '\1_\2')
         .tr("-", "_")