diff --git a/ChangeLog b/ChangeLog
index 705f848da..31b750405 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Feb 17  4:06:00 1999  Richard Frith-Macdonald <richard@brainstorm.co.uk>
+
+	* Source/NSApplication.m: ([-setDelegate:]) remove old delegate as
+	observer of application notifications.
+	* Source/NSWindow.m: ([-setDelegate:]) add delegate as observer for
+	window notifications.
+
 Tue Feb 16 17:06:00 1999  Richard Frith-Macdonald <richard@brainstorm.co.uk>
 
 	Additions provided by mgiddings@ypc.net -
diff --git a/Source/NSApplication.m b/Source/NSApplication.m
index 1204a02e5..c30543019 100644
--- a/Source/NSApplication.m
+++ b/Source/NSApplication.m
@@ -1649,6 +1649,8 @@ BOOL done = NO;
 {
   NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
 
+  if (delegate)
+    [nc removeObserver: delegate name: nil object: self];
   delegate = anObject;
 
 #define SET_DELEGATE_NOTIFICATION(notif_name) \
diff --git a/Source/NSWindow.m b/Source/NSWindow.m
index bf3562b8c..a849aab30 100644
--- a/Source/NSWindow.m
+++ b/Source/NSWindow.m
@@ -1180,8 +1180,40 @@ id result = nil;
 //
 // Assigning a delegate
 //
-- delegate                                      { return delegate; }
-- (void)setDelegate:anObject                    { delegate = anObject; }
+- (id) delegate
+{
+  return delegate;
+}
+
+- (void) setDelegate: (id)anObject
+{
+  NSNotificationCenter	*nc = [NSNotificationCenter defaultCenter];
+
+  if (delegate)
+    [nc removeObserver: delegate name: nil object: self];
+  delegate = anObject;
+
+#define SET_DELEGATE_NOTIFICATION(notif_name) \
+  if ([delegate respondsToSelector:@selector(window##notif_name:)]) \
+    [nc addObserver:delegate \
+      selector:@selector(window##notif_name:) \
+      name:NSWindow##notif_name##Notification object:self]
+
+  SET_DELEGATE_NOTIFICATION(DidBecomeKey);
+  SET_DELEGATE_NOTIFICATION(DidBecomeMain);
+  SET_DELEGATE_NOTIFICATION(DidChangeScreen);
+  SET_DELEGATE_NOTIFICATION(DidDeminiaturize);
+  SET_DELEGATE_NOTIFICATION(DidExpose);
+  SET_DELEGATE_NOTIFICATION(DidMiniaturize);
+  SET_DELEGATE_NOTIFICATION(DidMove);
+  SET_DELEGATE_NOTIFICATION(DidResignKey);
+  SET_DELEGATE_NOTIFICATION(DidResignMain);
+  SET_DELEGATE_NOTIFICATION(DidResize);
+  SET_DELEGATE_NOTIFICATION(DidUpdate);
+  SET_DELEGATE_NOTIFICATION(WillClose);
+  SET_DELEGATE_NOTIFICATION(WillMiniaturize);
+  SET_DELEGATE_NOTIFICATION(WillMove);
+}
 
 //
 // Implemented by the delegate