diff --git a/TL866_Updater/QT/hexwriter.h b/TL866_Updater/QT/hexwriter.h
index c4f1f4b..bd9b757 100644
--- a/TL866_Updater/QT/hexwriter.h
+++ b/TL866_Updater/QT/hexwriter.h
@@ -5,7 +5,7 @@
 class HexWriter
 {
 public:
-    HexWriter(QIODevice *file);
+    explicit HexWriter(QIODevice *file);
     void WriteHex(QByteArray data);
 
 private: