diff --git a/example/ex1/ex1.cpp b/example/ex1/ex1.cpp
index 2e286e7c..8909e188 100644
--- a/example/ex1/ex1.cpp
+++ b/example/ex1/ex1.cpp
@@ -5,13 +5,17 @@
 
 int
 main () {
+    namespace u = xo::unit::units;
     namespace qty = xo::unit::qty;
+    using xo::unit::quantity;
     using namespace std;
 
     auto t = qty::milliseconds(10);
     auto m = qty::kilograms(2.5);
     auto a = m / (t*t);
 
+    static_assert(same_as<decltype(t), quantity<u::millisecond, int>>);
+
     cerr << "t: " << t << ", m: " << m << ", m.t^-2: " << a << endl;
 }