diff --git a/pkgs/racket-test-core/tests/racket/unicode.rktl b/pkgs/racket-test-core/tests/racket/unicode.rktl
index eb2aa1c6de..92e3e212e6 100644
--- a/pkgs/racket-test-core/tests/racket/unicode.rktl
+++ b/pkgs/racket-test-core/tests/racket/unicode.rktl
@@ -1724,4 +1724,10 @@
 
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(test #\uFFFF bytes-utf-8-ref #"\357\277\277" 0)
+(test #f bytes-utf-8-ref #"\357\277" 0)
+(test #\nul bytes-utf-8-ref #"\357\277" 0 #\nul)
+
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
 (report-errs)
diff --git a/racket/src/racket/src/string.c b/racket/src/racket/src/string.c
index 47b57f751d..c09808a9d0 100644
--- a/racket/src/racket/src/string.c
+++ b/racket/src/racket/src/string.c
@@ -1587,11 +1587,11 @@ byte_string_utf8_ref(int argc, Scheme_Object *argv[])
   utf8_decode_x((unsigned char *)chars, istart, ifinish,
 		us, 0, 1,
 		&ipos, &opos,
-		0, 0, NULL, 0, perm ? 0xFFFF : 0);
+		0, 0, NULL, 0, perm ? 0xFFFFFF : 0);
 
   if (opos < 1)
     return scheme_false;
-  else if (us[0] == 0xFFFF)
+  else if (us[0] == 0xFFFFFF)
     return perm;
   else
     return scheme_make_character(us[0]);