diff --git a/conversation.rkt b/conversation.rkt
index 9927b63..eb0336a 100644
--- a/conversation.rkt
+++ b/conversation.rkt
@@ -29,18 +29,19 @@
 
 (struct credit (who amount) #:prefab) ;; give someone an amount of credit
 
-(struct room (name ch members) #:transparent)
+(struct room (ch))
 (struct blocking-box (ch))
 
+(struct room-state (name ch members) #:transparent)
 (struct binding (name in-ch out-ch disconnect-box queue-box thread) #:transparent)
 
 (define (make-room [name (gensym 'room)])
   (define ch (make-channel))
-  (thread (lambda () (room-main (room name ch '()))))
-  ch)
+  (thread (lambda () (room-main (room-state name ch '()))))
+  (room ch))
 
 (define (join-room room [name (gensym 'peer)])
-  (make-object membership% room name))
+  (make-object membership% (room-ch room) name))
 
 (define (make-blocking-box)
   (blocking-box (make-channel)))
@@ -141,14 +142,14 @@
 			     (handle-evt (thread-dead-evt (binding-thread b))
 					 (lambda (dummy)
 					   (room-main (part state b 'EXIT))))))
-	       (handle-evt (room-ch state)
+	       (handle-evt (room-state-ch state)
 			   (match-lambda
 			    (`(join ,name ,in-ch ,out-ch ,disconnect-box ,thread)
 			     (room-main (join state name in-ch out-ch disconnect-box thread)))
 			    (unexpected (log-warning (format "room-main: unexpected message ~v"
 							     unexpected))
 					(room-main state))))
-	       (room-members state))))
+	       (room-state-members state))))
 
 (define (handle-binding-message state b message)
   (match message
@@ -170,21 +171,21 @@
 
 (define (membership-summary state)
   (map (lambda (member) (arrived (binding-name member)))
-       (room-members state)))
+       (room-state-members state)))
 
 (define (add-binding state b)
-  (struct-copy room state
-	       [members (cons b (room-members state))]))
+  (struct-copy room-state state
+	       [members (cons b (room-state-members state))]))
 
 (define (remove-binding state b)
-  (struct-copy room state
-	       [members (remove b (room-members state) eq?)]))
+  (struct-copy room-state state
+	       [members (remove b (room-state-members state) eq?)]))
 
 (define (broadcast state b message)
   (for-each (lambda (member)
 	      (when (not (eq? member b))
 		(enqueue-message! member message)))
-	    (room-members state))
+	    (room-state-members state))
   state)
 
 (define (enqueue-message! b message)