diff --git a/collects/mred/private/kernel.ss b/collects/mred/private/kernel.ss
index 4a5744a4..3b5938b9 100644
--- a/collects/mred/private/kernel.ss
+++ b/collects/mred/private/kernel.ss
@@ -520,6 +520,7 @@
     on-toolbar-click
     on-menu-click
     on-menu-command
+    on-mdi-activate
     enforce-size
     on-close
     on-activate
diff --git a/collects/mred/private/mrtop.ss b/collects/mred/private/mrtop.ss
index f7287d9d..84d74122 100644
--- a/collects/mred/private/mrtop.ss
+++ b/collects/mred/private/mrtop.ss
@@ -160,6 +160,7 @@
 		       (lambda (e)
 			 (check-instance '(method frame% on-menu-char) wx:key-event% 'key-event% #f e)
 			 (send wx handle-menu-key e)))]
+	[on-mdi-activate (lambda (on?) (void))]
 	[on-toolbar-button-click (lambda () (void))]
 	[create-status-line (entry-point (lambda () (unless status-line? (send wx create-status-line) (set! status-line? #t))))]
 	[set-status-text (lambda (s) (send wx set-status-text s))]
diff --git a/collects/mred/private/wxtop.ss b/collects/mred/private/wxtop.ss
index 80bcfcf1..a310f2f7 100644
--- a/collects/mred/private/wxtop.ss
+++ b/collects/mred/private/wxtop.ss
@@ -628,7 +628,14 @@
 	 [on-toolbar-click 
 	  (entry-point
 	   (lambda ()
-	     (as-exit (lambda () (send (wx->mred this) on-toolbar-button-click)))))])
+	     (as-exit (lambda () (send (wx->mred this) on-toolbar-button-click)))))]
+	 [on-mdi-activate
+	  (entry-point
+	   (lambda (on?)
+	     (let ([mr (wx->mred this)])
+	       (queue-window-callback
+		this
+		(lambda () (send mr on-mdi-activate on?))))))])
        (public
 	 [handle-menu-key
 	  (lambda (event)