diff --git a/turnstile/examples/stlc+union.rkt b/turnstile/examples/stlc+union.rkt
index b209778..40f1710 100644
--- a/turnstile/examples/stlc+union.rkt
+++ b/turnstile/examples/stlc+union.rkt
@@ -59,7 +59,7 @@
      #:with tys- (prune+sort #'(ty1- ... ... ty2- ...))
      (if (= 1 (stx-length #'tys-))
          (stx-car #'tys-)
-         #'(U* . tys-))]))
+         (syntax/loc stx (U* . tys-)))]))
 (define-syntax Bool
   (make-variable-like-transformer
    (add-orig #'(U False True) #'Bool)))