diff --git a/collects/tests/drracket/random.rkt b/collects/tests/drracket/random.rkt
new file mode 100644
index 0000000000..3a5dca227e
--- /dev/null
+++ b/collects/tests/drracket/random.rkt
@@ -0,0 +1,59 @@
+#lang racket
+
+(require "private/drracket-test-util.rkt"
+         tests/utils/gui
+         mred
+         framework
+         (prefix-in fw: framework))
+
+(define (run-test)
+  (define dr (wait-for-drscheme-frame))
+  
+  (clear-definitions dr)
+  (insert-in-definitions dr (file->string "/home/mflatt/svn/mflatt/text/expmodel/mm-defs.rkt"))
+
+  (let loop ()
+    (define n (random 100))
+    (cond
+     [(n . < . 10)
+      (test:keystroke #\A)
+      (test:keystroke #\backspace)]
+     [(n . < . 50)
+      (test:keystroke 'left)]
+     [(n . < . 60)
+      (test:keystroke 'up)]
+     [(n . < . 70)
+      (test:keystroke 'down)]
+     [(n . < . 80)
+      (test:keystroke 'right)]
+     [(n . < . 82)
+      (sleep 10)]
+     [(n . < . 83)
+      (test:keystroke 'f5)
+      (test:keystroke #\x '(control))
+      (test:keystroke #\o)]
+     [else
+      (test:keystroke 'left)
+      (test:keystroke 'right)
+      (test:keystroke #\backspace)
+      (test:keystroke #\z '(meta))])
+    (sleep 0.25)
+    (loop)))
+
+(dynamic-require 'drscheme #f)
+      
+(fw:test:use-focus-table #t)
+
+(thread (λ () 
+           (let ([orig-display-handler (error-display-handler)])
+             (uncaught-exception-handler
+              (λ (x)
+                 (if (exn? x)
+                     (orig-display-handler (exn-message x) x)
+                     (fprintf (current-error-port) "uncaught exception ~s\n" x))
+                 (exit 1))))
+           (run-test)
+           (exit)))
+(yield (make-semaphore 0))
+
+
diff --git a/src/racket/src/thread.c b/src/racket/src/thread.c
index a46fc953d1..b76342bea0 100644
--- a/src/racket/src/thread.c
+++ b/src/racket/src/thread.c
@@ -4600,7 +4600,7 @@ void scheme_thread_block(float sleep_time)
   skip_sleep = 0;
   if (check_fd_semaphores()) {
     /* double check whether a semaphore for this thread woke up: */
-    if (p->block_descriptor == GENERIC_BLOCKED) {
+    if (!do_atomic && (p->block_descriptor == GENERIC_BLOCKED)) {
       if (p->block_check) {
         Scheme_Ready_Fun_FPC f = (Scheme_Ready_Fun_FPC)p->block_check;
         Scheme_Schedule_Info sinfo;