diff --git a/examples/hello.quox b/examples/hello.quox
index 8e5dbf9..db220cf 100644
--- a/examples/hello.quox
+++ b/examples/hello.quox
@@ -21,4 +21,6 @@ postulate print : String → IO Unit
 load "nat.quox"
 
 #[main]
-def main = seq (print-ℕ (nat.plus 60 9)) (print "(nice)")
+def main : IO Unit =
+  let1 sixty-nine = nat.plus 60 9 in
+  seq (print-ℕ sixty-nine) (print "(nice)")