diff --git a/include/argparse/argparse.hpp b/include/argparse/argparse.hpp
index 7f285b2..4439488 100644
--- a/include/argparse/argparse.hpp
+++ b/include/argparse/argparse.hpp
@@ -73,7 +73,7 @@ struct is_streamable : std::false_type {};
 
 template <typename T>
 struct is_streamable<
-    T, std::void_t<decltype(std::declval<std::ostream>() << std::declval<T>())>>
+    T, std::void_t<decltype(std::declval<std::ostream&>() << std::declval<T>())>>
   : std::true_type {};
 
 template <typename T>