diff --git a/include/argparse.hpp b/include/argparse.hpp
index c8dfdc6..0b6c1eb 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -44,6 +44,7 @@ SOFTWARE.
 
 namespace argparse {
 
+namespace { // anonymous namespace for helper methods - not visible outside this header file
 // Some utility structs to check template specialization
 template<typename Test, template<typename...> class Ref>
 struct is_specialization : std::false_type {};
@@ -67,6 +68,7 @@ T get_from_list(const std::list<T>& aList, size_t aIndex) {
   }
   return T();
 }
+}
 
 class Argument {
   friend class ArgumentParser;