diff --git a/racket/syndicate/examples/actor/fs-shell.rkt b/racket/syndicate/examples/actor/fs-shell.rkt
index 7755a64..bf68ec7 100644
--- a/racket/syndicate/examples/actor/fs-shell.rkt
+++ b/racket/syndicate/examples/actor/fs-shell.rkt
@@ -17,16 +17,14 @@
   (define (print-prompt)
     (printf "> ")
     (flush-output))
-  (define reader-count 0)
-  (define (generate-reader-id)
-    (begin0 reader-count
-      (set! reader-count (+ reader-count 1))))
-  (actor (print-prompt)
+  (actor (field [reader-count 0])
+         (print-prompt)
          (until (message (inbound (external-event e (list (? eof-object? _)))))
                 (on (message (inbound (external-event e (list (? bytes? $bs)))))
                     (match (string-split (string-trim (bytes->string/utf-8 bs)))
                       [(list "open" name)
-                       (define reader-id (generate-reader-id))
+                       (define reader-id (reader-count))
+                       (reader-count (+ (reader-count) 1))
                        (actor (printf "Reader ~a opening file ~v.\n" reader-id name)
                               (until (message `(stop-watching ,name))
                                      (on (asserted (file name $contents))