diff --git a/include/str_utility.hpp b/include/str_utility.hpp
index 12e51f8..31c44b4 100644
--- a/include/str_utility.hpp
+++ b/include/str_utility.hpp
@@ -3,6 +3,7 @@
 #pragma once
 
 #include <algorithm>
+#include <cstddef>
 #include <ranges>
 #include <string>
 #include <string_view>