diff --git a/pkgs/racket-test-core/tests/racket/port.rktl b/pkgs/racket-test-core/tests/racket/port.rktl
index f5d469174c..dc30033615 100644
--- a/pkgs/racket-test-core/tests/racket/port.rktl
+++ b/pkgs/racket-test-core/tests/racket/port.rktl
@@ -934,6 +934,35 @@
   (check-all void)
   (check-all port-count-lines!))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; attempting to read from or write to a closed byte-string port
+
+(let ()
+  (define (check proc)
+    (define p (open-input-bytes #"x"))
+    (close-input-port p)
+    (err/rt-test (proc p) exn:fail:contract? #rx"closed"))
+  (check read-byte)
+  (check peek-byte)
+  (check (lambda (p) (peek-byte p 10)))
+  (check (lambda (p) (read-bytes 10 p)))
+  (check read-char)
+  (check read-char-or-special)
+  (check peek-char)
+  (check (lambda (p) (read-string 10 p)))
+  (check read)
+  (check (lambda (p) (read-syntax (object-name p) p))))
+
+(let ()
+  (define (check proc)
+    (define p (open-output-bytes))
+    (close-output-port p)
+    (err/rt-test (proc p) exn:fail:contract? #rx"closed"))
+  (check (lambda (p) (write-byte 10 p)))
+  (check (lambda (p) (write-bytes #"hello" p)))
+  (check (lambda (p) (write-char #\x p)))
+  (check (lambda (p) (write-string "hello" p))))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; port-closed events
 
diff --git a/racket/src/cs/schemified/io.scm b/racket/src/cs/schemified/io.scm
index 7382a1621c..9f3d786f2d 100644
--- a/racket/src/cs/schemified/io.scm
+++ b/racket/src/cs/schemified/io.scm
@@ -18500,9 +18500,11 @@
                   (set-bytes-input-port-bstr! this-id_0 #f)
                   (let ((b_0 (core-port-buffer this-id_0)))
                     (if (direct-bstr b_0)
-                      (begin
-                        (set-core-port-offset! this-id_0 (direct-pos b_0))
-                        (set-direct-bstr! b_0 #f))
+                      (let ((pos_0 (direct-pos b_0)))
+                        (begin
+                          (set-core-port-offset! this-id_0 pos_0)
+                          (set-direct-end! b_0 pos_0)
+                          (set-direct-bstr! b_0 #f)))
                       (void)))))))))
        app_0
        app_1
diff --git a/racket/src/io/port/bytes-port.rkt b/racket/src/io/port/bytes-port.rkt
index a397981f26..7fa22bff62 100644
--- a/racket/src/io/port/bytes-port.rkt
+++ b/racket/src/io/port/bytes-port.rkt
@@ -45,7 +45,9 @@
      (set! bstr #f)
      (define b buffer)
      (when (direct-bstr b)
-       (set! offset (direct-pos b))
+       (define pos (direct-pos b))
+       (set! offset pos)
+       (set-direct-end! b pos)
        (set-direct-bstr! b #f)))]
   [file-position
    (case-lambda