diff --git a/os-big-bang.rkt b/os-big-bang.rkt
index b705388..47f498f 100644
--- a/os-big-bang.rkt
+++ b/os-big-bang.rkt
@@ -59,17 +59,19 @@
 
 (define-syntax message-handlers
   (syntax-rules ()
-    ((_ old-state [pattern body ...] ...)
+    ((_ old-state-pattern [pattern body ...] ...)
      (on-message (match-lambda [pattern #t] ... [_ #f])
 		 (lambda (message old-state)
+		   (match-define old-state-pattern old-state)
 		   (match message
 		     [pattern body ...] ...))))))
 
 (define-syntax meta-message-handler
   (syntax-rules (=>)
-    ((_ old-state [(raw-pattern => pattern) body ...])
+    ((_ old-state-pattern [(raw-pattern => pattern) body ...])
      (on-meta-message raw-pattern
 		      (lambda (meta-message old-state)
+			(match-define old-state-pattern old-state)
 			(match meta-message
 			  [pattern body ...]))))))