diff --git a/os.rkt b/os.rkt
index aa6e6db..5d9c6bd 100644
--- a/os.rkt
+++ b/os.rkt
@@ -113,7 +113,7 @@
 
 ;; A MessageHandler is one of
 ;; -- (message-handler MessagePattern TrapK<Message>)
-(struct message-handler (matcher k) #:transparent)
+(struct message-handler (pattern k) #:transparent)
 
 ;; A KernelModeTransition is a
 ;; (kernel-mode-transition Subscription
@@ -225,7 +225,7 @@
       ;; back on the list for some future message.
       (subscribe-process sub state)]
      [((apply-getter (vm-vtable state))
-       (message-handler-matcher (car message-handlers))
+       (message-handler-pattern (car message-handlers))
        message)
       (perform-transition ((message-handler-k (car message-handlers))
 			   (subscription-state sub))
@@ -262,7 +262,7 @@
 			  '()))
 
 (define (wrap-meta-message-handler mh)
-  (message-handler (message-handler-matcher mh) dispatch-meta-message))
+  (message-handler (message-handler-pattern mh) dispatch-meta-message))
 
 (define ((dispatch-meta-message message) state)
   (run-vm