diff --git a/include/Arg.hpp b/include/Arg.hpp
index 4809ff1..2ea3f92 100644
--- a/include/Arg.hpp
+++ b/include/Arg.hpp
@@ -107,7 +107,7 @@ class Arg {
     // auto_env_name_
     // [[nodiscard]] inline const std::string get__auto_env_name() const {
     //   std::string env_name = PROGRAM_NAME() + '_' + this->get__name();
-    //   std::transform(env_name.begin(), env_name.end(), env_name.begin(), [](const unsigned char& c) { return std::toupper(c); });
+    //   to_upper(env_name);
     //   return env_name;
     // }
 
diff --git a/include/utils.hpp b/include/utils.hpp
index cfd0dec..387a618 100644
--- a/include/utils.hpp
+++ b/include/utils.hpp
@@ -1,9 +1,10 @@
 #pragma once
 
+#include <algorithm>
 #include <optional>
+#include <sstream>
 #include <stdexcept>
 #include <string>
-#include <sstream>
 
 template <typename T, typename E>
 inline T ok_or(std::optional<T> opt, E&& err) {
@@ -44,3 +45,7 @@ inline void print_indent(std::ostream& os, int indent_level) {
     for (int i = 0; i < indent_level; ++i)
         os << '\t';
 }
+
+inline void to_upper(std::string &s) {
+    std::ranges::transform(s, s.begin(), [](const unsigned char& c) { return std::toupper(c); });
+}
diff --git a/src/Parser.cpp b/src/Parser.cpp
index dcdfc44..31c44e0 100644
--- a/src/Parser.cpp
+++ b/src/Parser.cpp
@@ -63,7 +63,7 @@ void ClapParser::check_env() {
     for (auto& arg : args_) {
         if (arg.get__auto_env()) {
             std::string env_name = this->program_name_ + '_' + arg.get__name();
-            std::transform(env_name.begin(), env_name.end(), env_name.begin(), [](const unsigned char& c) { return std::toupper(c); });
+            to_upper(env_name);
             auto value_from_env = std::getenv(env_name.c_str());
             if (value_from_env) {
                 arg.set__value(value_from_env);