diff --git a/racket/syndicate/drivers/filesystem.rkt b/racket/syndicate/drivers/filesystem.rkt
index 9e209d9..7ef95e6 100644
--- a/racket/syndicate/drivers/filesystem.rkt
+++ b/racket/syndicate/drivers/filesystem.rkt
@@ -20,29 +20,24 @@
   (spawn #:name 'filesystem-driver
          (during/spawn (observe (file-content $name $reader-proc _))
            #:name (list 'file-content name reader-proc)
-           (track-file name reader-proc))))
+           (track-file name reader-proc))
+         (during (observe (inbound (file-changed $name)))
+           (monitor-thread name))))
 
 (define (read-file name reader-proc)
   (and (or (file-exists? name) (directory-exists? name))
        (reader-proc name)))
 
+(define (path->parent-path name)
+  (let-values (((parent-path _leaf _syntactically-dir?)
+                (split-path (path->complete-path name))))
+    parent-path))
+
 (define (track-file name reader-proc)
-  (define control-ch (make-channel))
-
-  (define parent-path
-    (let-values (((parent-path _leaf _syntactically-dir?)
-                  (split-path (path->complete-path name))))
-      parent-path))
-
-  (thread (lambda () (track-file-changes name parent-path control-ch)))
-
   (field [content (read-file name reader-proc)])
-
   (assert (file-content name reader-proc (content)))
-
   (on (message (inbound (file-changed name)))
       (content (read-file name reader-proc)))
-
   ;; This horrible hack is required to work around limitations in the
   ;; OS's file-change reporting. It seems (?) as if, monitoring both
   ;; "a/b" and "a/", that only the event for "a/" will be fired when
@@ -56,30 +51,32 @@
   ;; file-container-changed events for ALL recursive parents of the
   ;; path of interest up to the root.
   ;;
-  (on (message (inbound (file-container-changed parent-path)))
-      (content (read-file name reader-proc)))
+  (on (message (inbound (file-container-changed (path->parent-path name))))
+      (content (read-file name reader-proc))))
 
+(define (monitor-thread name)
+  (define control-ch (make-channel))
+  (thread (lambda ()
+            (define parent-path (path->parent-path name))
+            (let loop ()
+              (sync (handle-evt control-ch
+                                (lambda (msg)
+                                  ;; (log-info "track-file-changes ~v: ~v" name msg)
+                                  (match msg
+                                    ['quit (void)])))
+                    (if (or (file-exists? name) (directory-exists? name)) ;; TODO: TOCTTOU :-(
+                        (handle-evt (filesystem-change-evt name)
+                                    (lambda (_dummy)
+                                      ;; (log-info "track-file-changes ~v: changed" name)
+                                      (send-ground-message (file-changed name))
+                                      (loop)))
+                        (handle-evt (filesystem-change-evt parent-path)
+                                    (lambda (_dummy)
+                                      ;; (log-info "track-file-changes ~v: directory changed" name)
+                                      (send-ground-message (file-container-changed parent-path))
+                                      (loop))))))))
   (on-stop (channel-put control-ch 'quit)))
 
-(define (track-file-changes name parent-path control-ch)
-  (let loop ()
-    (sync (handle-evt control-ch
-                      (lambda (msg)
-                        ;; (log-info "track-file-changes ~v: ~v" name msg)
-                        (match msg
-                          ['quit (void)])))
-          (if (or (file-exists? name) (directory-exists? name)) ;; TODO: TOCTTOU :-(
-              (handle-evt (filesystem-change-evt name)
-                          (lambda (_dummy)
-                            ;; (log-info "track-file-changes ~v: changed" name)
-                            (send-ground-message (file-changed name))
-                            (loop)))
-              (handle-evt (filesystem-change-evt parent-path)
-                          (lambda (_dummy)
-                            ;; (log-info "track-file-changes ~v: directory changed" name)
-                            (send-ground-message (file-container-changed parent-path))
-                            (loop)))))))
-
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (spawn-filesystem-driver)
diff --git a/racket/syndicate/examples/actor/make.rkt b/racket/syndicate/examples/actor/make.rkt
new file mode 100644
index 0000000..9d18565
--- /dev/null
+++ b/racket/syndicate/examples/actor/make.rkt
@@ -0,0 +1,28 @@
+#lang syndicate
+;; Automagic "make"-like utility.
+
+(require/activate syndicate/drivers/filesystem)
+(require racket/string)
+(require racket/system)
+(require file/sha1)
+
+(define (file->sha1 p)
+  (call-with-input-file p sha1))
+
+(spawn (during (observe (file-content $name _ _))
+         (when (not (string-suffix? name ".c"))
+           (define name.c (string-append name ".c"))
+           (on-start (printf "Tracking ~a, to see if we can use it to build ~a\n" name.c name))
+           (during (file-content name.c file->sha1 $hash) ;; nb. $hash, not _
+             (on-start
+              (if hash
+                  (begin (printf "~a has changed hash to ~a, recompiling\n" name.c hash)
+                         (system* (find-executable-path "cc") "-o" name name.c))
+                  (printf "~a doesn't exist.\n" name.c)))))))
+
+(spawn (on (asserted (file-content "." directory-list $files))
+           (for [(name-path (in-list files))]
+             (match (path->string name-path)
+               [(pregexp #px"(.*)\\.c" (list _ name))
+                (assert! (observe (file-content name file-exists? #t)))]
+               [_ (void)]))))