diff --git a/collects/2htdp/private/last.ss b/collects/2htdp/private/last.ss
index e38362ae54..b87bf1797c 100644
--- a/collects/2htdp/private/last.ss
+++ b/collects/2htdp/private/last.ss
@@ -6,6 +6,7 @@
 
 (define last-mixin
   (mixin (start-stop<%>) ()
+    ;; to comunicate between stop! and last
     (field [end:ch  (make-channel)])
 
     ;; X -> Void
@@ -15,7 +16,7 @@
     
     ;; -> World
     (define/public (last) 
-      (define result (yield end:ch))
+      (define result (sync #;yield end:ch)) ;; bug? 
       (if (exn? result) (raise result) result))
     
     (field [dr:cust (current-custodian)])
@@ -24,7 +25,9 @@
     ;; send x to last method
     (define/private (send-to-last x)
       (parameterize ((current-custodian dr:cust))
-        (thread (lambda () (channel-put end:ch x)))))
+        (thread 
+         (lambda ()
+           (channel-put end:ch x)))))
     
     (super-new)))
     
diff --git a/collects/2htdp/private/launch-many-worlds.ss b/collects/2htdp/private/launch-many-worlds.ss
index 063151eda9..7049734e6d 100644
--- a/collects/2htdp/private/launch-many-worlds.ss
+++ b/collects/2htdp/private/launch-many-worlds.ss
@@ -19,8 +19,7 @@
          [ch (make-channel)]
          [pu (curry channel-put ch)]
          [th (map (lambda (th i)
-                    (parameterize ([current-custodian c*]
-                                   [current-eventspace (make-eventspace)])
+                    (parameterize ([current-custodian c*])
                       (rec t
                         (thread
                          (lambda ()
diff --git a/collects/2htdp/uchat/chatter.ss b/collects/2htdp/uchat/chatter.ss
index 174913c754..3cddb0a12e 100644
--- a/collects/2htdp/uchat/chatter.ss
+++ b/collects/2htdp/uchat/chatter.ss
@@ -1,7 +1,7 @@
 ;; The first three lines of this file were inserted by DrScheme. They record metadata
 ;; about the language level of this file in a form that our tools can easily process.
-#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname chatter) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
-(require 2htdp/universe)
+#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname chatter) (read-case-sensitive #t) (teachpacks ((lib "universe.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "universe.ss" "teachpack" "2htdp")))))
+;(require 2htdp/universe)
 (require "auxiliaries.ss")
 
 #|
@@ -480,5 +480,6 @@
             (on-key react)
             (on-draw render)
             (on-receive receive)
+            (check-with world?)
             (name n)
             (register LOCALHOST)))
diff --git a/collects/2htdp/universe.ss b/collects/2htdp/universe.ss
index 909d36442e..4cc9867e3e 100644
--- a/collects/2htdp/universe.ss
+++ b/collects/2htdp/universe.ss
@@ -170,8 +170,9 @@
                                        kwds Spec)))
                          (list (syntax-e (car co)) ((cadr co) (cdr x))))
                        spec)])
-       #`(let ([o (new (if #,rec? aworld% world%) [world0 w]  #,@args)])
-           (send o last)))]))
+       #`(parameterize ([current-eventspace (make-eventspace)])
+           (let ([o (new (if #,rec? aworld% world%) [world0 w]  #,@args)])
+             (send o last))))]))
 
 
 ;                                                                 
@@ -320,5 +321,6 @@
          [(not (memq 'on-msg domain))
           (raise-syntax-error #f "missing on-msg clause" stx)]
          [else ; (and (memq #'on-new domain) (memq #'on-msg domain))
-          #`(send (new universe% [universe0 u] #,@args) last)]))]))
+          #`(parameterize ([current-eventspace (make-eventspace)])
+              (send (new universe% [universe0 u] #,@args) last))]))]))