diff --git a/mozilla/widget/src/cocoa/nsChildView.mm b/mozilla/widget/src/cocoa/nsChildView.mm
index 4940b118a89..cc2520c12e3 100644
--- a/mozilla/widget/src/cocoa/nsChildView.mm
+++ b/mozilla/widget/src/cocoa/nsChildView.mm
@@ -2373,7 +2373,8 @@ nsChildView::Idle()
     [self removeTrackingRect:mMouseEnterExitTag];
 
   mMouseEnterExitTag = [self addTrackingRect:[self bounds] owner:self
-                                    userData:nil assumeInside: YES];
+                                    userData:nil assumeInside: [[self window]
+                                    acceptsMouseMovedEvents]];
 }
 
 
@@ -2446,7 +2447,8 @@ nsChildView::Idle()
     mGeckoChild->AddedToWindow();
 
   mMouseEnterExitTag = [self addTrackingRect:[self bounds] owner:self
-                                    userData:nil assumeInside: YES];
+                                    userData:nil assumeInside: [[self window]
+                                    acceptsMouseMovedEvents]];
 }
 
 - (void)viewWillStartLiveResize