diff --git a/collects/tests/racket/unsafe.rktl b/collects/tests/racket/unsafe.rktl
index 84e9c82ff0..3694279716 100644
--- a/collects/tests/racket/unsafe.rktl
+++ b/collects/tests/racket/unsafe.rktl
@@ -307,15 +307,24 @@
               #:literal-ok? #f))
   (test-bin 65535 'unsafe-u16vector-ref (u16vector 10 65535 187) 1)
 
-  (for ([star (list values (add-star "star"))])
+  (let ()
     (define-struct posn (x [y #:mutable] z))
-    (test-bin 'a unsafe-struct-ref (make-posn 'a 'b 'c) 0 #:literal-ok? #f)
-    (test-bin 'b unsafe-struct-ref (make-posn 'a 'b 'c) 1 #:literal-ok? #f)
-    (let ([p (make-posn 100 200 300)])
+    (for ([star (list values (add-star "star"))])
+      (test-bin 'a unsafe-struct-ref (make-posn 'a 'b 'c) 0 #:literal-ok? #f)
+      (test-bin 'b unsafe-struct-ref (make-posn 'a 'b 'c) 1 #:literal-ok? #f)
+      (let ([p (make-posn 100 200 300)])
+        (test-tri 500 (star 'unsafe-struct-set!) p 1 500
+                  #:pre (lambda () (set-posn-y! p 0)) 
+                  #:post (lambda (x) (posn-y p))
+                  #:literal-ok? #f)))
+    (let ([p (chaperone-struct (make-posn 100 200 300)
+                               posn-y (lambda (p v) v)
+                               set-posn-y! (lambda (p v) v))])
       (test-tri 500 'unsafe-struct-set! p 1 500
                 #:pre (lambda () (set-posn-y! p 0)) 
                 #:post (lambda (x) (posn-y p))
                 #:literal-ok? #f)))
+    
   ;; test unboxing:
   (test-tri 5.4 '(lambda (x y z) (unsafe-fl+ x (unsafe-f64vector-ref y z))) 1.2 (f64vector 1.0 4.2 6.7) 1)
   (test-tri 3.2 '(lambda (x y z) 
diff --git a/src/racket/src/vector.c b/src/racket/src/vector.c
index 0c114d6e44..08a9ea6ddb 100644
--- a/src/racket/src/vector.c
+++ b/src/racket/src/vector.c
@@ -887,12 +887,18 @@ static Scheme_Object *unsafe_vector_set (int argc, Scheme_Object *argv[])
 
 static Scheme_Object *unsafe_struct_ref (int argc, Scheme_Object *argv[])
 {
-  return ((Scheme_Structure *)argv[0])->slots[SCHEME_INT_VAL(argv[1])];
+  if (SCHEME_CHAPERONEP(argv[0]))
+    return scheme_struct_ref(argv[0], SCHEME_INT_VAL(argv[1]));
+  else
+    return ((Scheme_Structure *)argv[0])->slots[SCHEME_INT_VAL(argv[1])];
 }
 
 static Scheme_Object *unsafe_struct_set (int argc, Scheme_Object *argv[])
 {
-  ((Scheme_Structure *)argv[0])->slots[SCHEME_INT_VAL(argv[1])] = argv[2];
+  if (SCHEME_CHAPERONEP(argv[0]))
+    scheme_struct_set(argv[0], SCHEME_INT_VAL(argv[1]), argv[2]);
+  else
+    ((Scheme_Structure *)argv[0])->slots[SCHEME_INT_VAL(argv[1])] = argv[2];
   return scheme_void;
 }