diff --git a/collects/2htdp/private/check-aux.ss b/collects/2htdp/private/check-aux.ss
index b0a404c4d7..ff81e7b968 100644
--- a/collects/2htdp/private/check-aux.ss
+++ b/collects/2htdp/private/check-aux.ss
@@ -59,7 +59,7 @@
 (define (mouse-event->parts e)
   (define x (- (send e get-x) INSET))
   (define y (- (send e get-y) INSET))
-  (list x y (cond [(send e button-down?) 'button-down]
+  (values x y (cond [(send e button-down?) 'button-down]
                   [(send e button-up?)   'button-up]
                   [(send e dragging?)    'drag]
                   [(send e moving?)      'move]
diff --git a/collects/2htdp/private/world.ss b/collects/2htdp/private/world.ss
index 6daa9e326f..4e29a5882d 100644
--- a/collects/2htdp/private/world.ss
+++ b/collects/2htdp/private/world.ss
@@ -180,10 +180,12 @@
                    (when live (pkey (send e get-key-code))))
                  ;; deal with mouse events if live and within range 
                  (define/override (on-event e)
-                   (define l (mouse-event->parts e))
+                   (define-values (x y me) (mouse-event->parts e))
                    (when live
-                     (when (and (<= 0 (first l) width) (<= 0 (second l) height))
-                       (pmouse . l)))))
+                     (cond
+                       [(and (<= 0 x width) (<= 0 y height)) (pmouse x y me)]
+                       [(memq me '(leave enter)) (pmouse x y me)]
+                       [else (void)]))))
                (parent frame)
                (editor visible)
                (style '(no-hscroll no-vscroll))