diff --git a/example/include/validated_type.h b/example/include/validated_type.h
index 2cf8cc715..2f09563db 100644
--- a/example/include/validated_type.h
+++ b/example/include/validated_type.h
@@ -25,6 +25,7 @@
 #include <gsl/gsl-lite.hpp>
 #include <mp-units/bits/external/hacks.h>
 #include <mp-units/bits/fmt.h>
+#include <mp-units/customization_points.h>
 #include <ostream>
 #include <utility>
 
@@ -100,6 +101,9 @@ class validated_type {
   = default;
 };
 
+template<typename T, typename Validator>
+inline constexpr bool mp_units::is_scalar<validated_type<T, Validator>> = mp_units::is_scalar<T>;
+
 
 template<typename CharT, typename Traits, typename T, typename Validator>
 std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os,