diff --git a/mozilla/widget/src/gtk2/nsWindow.cpp b/mozilla/widget/src/gtk2/nsWindow.cpp
index 65c2cef919c..42f360b0acb 100644
--- a/mozilla/widget/src/gtk2/nsWindow.cpp
+++ b/mozilla/widget/src/gtk2/nsWindow.cpp
@@ -227,6 +227,9 @@ static nsresult    initialize_prefs        (void);
 nsWindow *nsWindow::mLastDragMotionWindow = NULL;
 PRBool nsWindow::sIsDraggingOutOf = PR_FALSE;
 
+// the last window that had a MOUSE_ENTER event
+nsWindow *nsWindow::sLastMouseEnterWindow = nsnull;
+
 // This is the time of the last button press event.  The drag service
 // uses it as the time to start drags.
 guint32   nsWindow::mLastButtonPressTime = 0;
@@ -419,6 +422,10 @@ nsWindow::Destroy(void)
     if (mIsDestroyed || !mCreated)
         return NS_OK;
 
+    if (this == sLastMouseEnterWindow) {
+        sLastMouseEnterWindow = nsnull;
+    }
+
     LOG(("nsWindow::Destroy [%p]\n", (void *)this));
     mIsDestroyed = PR_TRUE;
     mCreated = PR_FALSE;
@@ -1889,6 +1896,14 @@ nsWindow::OnEnterNotifyEvent(GtkWidget *aWidget, GdkEventCrossing *aEvent)
     if (aEvent->subwindow != NULL)
         return;
 
+    // Do not fire MOUSE_ENTER event if the mouse pointer is not on it.
+    // In this case, enter_notify_event is not triggered by mouse.
+    if (aEvent->x < 0 || aEvent->y < 0 ||
+        aEvent->x >= mBounds.width || aEvent->y >= mBounds.height) {
+        return;
+    }
+    sLastMouseEnterWindow = this;
+
     nsMouseEvent event(PR_TRUE, NS_MOUSE_ENTER, this, nsMouseEvent::eReal);
 
     event.refPoint.x = nscoord(aEvent->x);
@@ -1909,6 +1924,16 @@ nsWindow::OnLeaveNotifyEvent(GtkWidget *aWidget, GdkEventCrossing *aEvent)
     if (aEvent->subwindow != NULL)
         return;
 
+    // Do not fire MOUSE_EXIT event if the last MOUSE_ENTER event was not for
+    // the leaving window, or the mouse pointer is still on the leaving window.
+    // In this case, leave_notify_event is not triggered by mouse.
+    if (this != sLastMouseEnterWindow ||
+        (aEvent->x >= 0 && aEvent->y >= 0 &&
+         aEvent->x < mBounds.width && aEvent->y < mBounds.height)) {
+        return;
+    }
+    sLastMouseEnterWindow = nsnull;
+
     nsMouseEvent event(PR_TRUE, NS_MOUSE_EXIT, this, nsMouseEvent::eReal);
 
     event.refPoint.x = nscoord(aEvent->x);
diff --git a/mozilla/widget/src/gtk2/nsWindow.h b/mozilla/widget/src/gtk2/nsWindow.h
index a4842ba04f9..6e6ea439a74 100644
--- a/mozilla/widget/src/gtk2/nsWindow.h
+++ b/mozilla/widget/src/gtk2/nsWindow.h
@@ -426,6 +426,9 @@ private:
     // drag in progress
     static PRBool DragInProgress(void);
 
+    // the last window that had a MOUSE_ENTER event
+    static nsWindow  *sLastMouseEnterWindow;
+
     void         ResetDragMotionTimer     (GtkWidget      *aWidget,
                                            GdkDragContext *aDragContext,
                                            gint           aX,