diff --git a/AppKit/CPApplication.j b/AppKit/CPApplication.j
index 1e7a618ae..64c49d71f 100644
--- a/AppKit/CPApplication.j
+++ b/AppKit/CPApplication.j
@@ -1181,7 +1181,9 @@ _CPRunModalLoop = function(anEvent)
     var theWindow = [anEvent window],
         modalSession = CPApp._currentSession;
 
-    if (theWindow == modalSession._window || [theWindow worksWhenModal])
+    if (theWindow == modalSession._window || 
+        [theWindow worksWhenModal] ||
+        [theWindow attachedSheet] == modalSession._window)
         [theWindow sendEvent:anEvent];
 }
 
diff --git a/AppKit/CPWindow/CPWindow.j b/AppKit/CPWindow/CPWindow.j
index 08ee7ec13..d10a203d7 100644
--- a/AppKit/CPWindow/CPWindow.j
+++ b/AppKit/CPWindow/CPWindow.j
@@ -2369,8 +2369,14 @@ CPTexturedBackgroundWindowMask
 
     [[CPNotificationCenter defaultCenter] postNotificationName:CPWindowWillBeginSheetNotification object:self];
     
-    // old behavior; in Cocoa, sheets are not modal by default
-    //[CPApp runModalForWindow:aSheet];
+    // if sheet is attached to a modal window, the sheet runs 
+    // as if itself and the parent window are modal
+    aSheet._isModal = NO;
+    if ([CPApp modalWindow]===self)
+    {
+        [CPApp runModalForWindow:aSheet];
+        aSheet._isModal = YES;
+    }
 
     [aSheet orderFront:self];
     [aSheet setFrame:startFrame display:YES animate:NO];
@@ -2454,6 +2460,9 @@ CPTexturedBackgroundWindowMask
     _sheetContext = nil;
     sheet._parentView = nil;
 
+    if (sheet._isModal)
+        [CPApp stopModal];
+
     if (delegate != nil && endSelector != nil)
         objj_msgSend(delegate, endSelector, sheet, returnCode, contextInfo);
 }