diff --git a/QuickLook.Plugin/QuickLook.Plugin.ThumbnailViewer/Helper.cs b/QuickLook.Plugin/QuickLook.Plugin.ThumbnailViewer/Helper.cs
index 6480d8d..425b1d9 100644
--- a/QuickLook.Plugin/QuickLook.Plugin.ThumbnailViewer/Helper.cs
+++ b/QuickLook.Plugin/QuickLook.Plugin.ThumbnailViewer/Helper.cs
@@ -1,4 +1,21 @@
-using System.IO;
+// Copyright © 2017-2025 QL-Win Contributors
+//
+// This file is part of QuickLook program.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+using System.IO;
 using System.Windows.Media.Imaging;
 
 namespace QuickLook.Plugin.ThumbnailViewer;