diff --git a/os2-example.rkt b/os2-example.rkt
index d3d3437..dca2360 100644
--- a/os2-example.rkt
+++ b/os2-example.rkt
@@ -19,9 +19,11 @@
   (write `(sleeping for ,delay milliseconds))
   (newline)
   (sleep delay (lambda ()
-		 (write `(awoke after ,delay milliseconds))
-		 (newline)
-		 (transition 'no-state (kill)))))
+		 (if (> delay 1500)
+		     (error 'example-process "Oh noes!")
+		     (begin (write `(awoke after ,delay milliseconds))
+			    (newline)
+			    (transition 'no-state (kill)))))))
 
 (define spy
   (lambda ()
diff --git a/os2.rkt b/os2.rkt
index 8f4f950..17f77dc 100644
--- a/os2.rkt
+++ b/os2.rkt
@@ -228,10 +228,11 @@
 	 [preaction
 	  (loop rest (perform-action pid preaction state) outbound-actions)])])))
 
-(define (send-to-user f . args)
+(define (send-to-user failure-proc f . args)
   ;; TODO: use this hook to find all the bits of code that will need
   ;; with-handlers and crash compensation.
-  (apply f args))
+  (with-handlers ([exn:fail? failure-proc])
+    (apply f args)))
 
 (define (perform-action pid preaction state)
   (match preaction
@@ -332,7 +333,12 @@
 
 (define (run-trapk state pid trap-k . args)
   (if trap-k
-      (run-ready state pid (apply send-to-user trap-k args))
+      (run-ready state pid (apply send-to-user
+				  (lambda (e) (lambda (process-state)
+						(transition process-state
+						  (kill #f e))))
+				  trap-k
+				  args))
       state))
 
 (define (maybe-transition->transition t)
@@ -343,14 +349,21 @@
 (define (run-ready state pid interrupt-k)
   (define old-process (hash-ref (vm-processes state) pid))
   (match-define (transition new-process-state actions)
-    (maybe-transition->transition (send-to-user interrupt-k (process-state old-process))))
+    (maybe-transition->transition (send-to-user (lambda (e)
+						  (transition (process-state old-process)
+						    (kill #f e)))
+						interrupt-k
+						(process-state old-process))))
   (struct-copy vm (enqueue-actions state pid actions)
 	       [processes (hash-set (vm-processes state) pid
 				    (struct-copy process old-process
 						 [state new-process-state]))]))
 
 (define (do-spawn spawning-pid thunk k state)
-  (match-define (transition initial-state initial-actions) (send-to-user thunk))
+  (match-define (transition initial-state initial-actions) (send-to-user (lambda (e)
+									   (transition #f
+									     (kill #f e)))
+									 thunk))
   (define new-pid (vm-next-process-id state))
   (run-trapk (struct-copy vm (enqueue-actions state new-pid initial-actions)
 			  [processes (hash-set (vm-processes state) new-pid (process new-pid