diff --git a/shell/source/win32/shlxthandler/thumbviewer/thumbviewer.cxx b/shell/source/win32/shlxthandler/thumbviewer/thumbviewer.cxx
index 3062f8402966..8d929e87e1e5 100644
--- a/shell/source/win32/shlxthandler/thumbviewer/thumbviewer.cxx
+++ b/shell/source/win32/shlxthandler/thumbviewer/thumbviewer.cxx
@@ -117,7 +117,7 @@ namespace internal
     }
 }
 
-class StreamOnZipBuffer : public IStream
+class StreamOnZipBuffer final : public IStream
 {
 public:
     StreamOnZipBuffer(const ZipFile::ZipContentBuffer_t& zip_buffer);