diff --git a/Machines/ZX8081/CharacterMapper.hpp b/Machines/ZX8081/CharacterMapper.hpp
index 1d2b996da..b78b66dfd 100644
--- a/Machines/ZX8081/CharacterMapper.hpp
+++ b/Machines/ZX8081/CharacterMapper.hpp
@@ -6,8 +6,8 @@
 //  Copyright © 2017 Thomas Harte. All rights reserved.
 //
 
-#ifndef CharacterMapper_hpp
-#define CharacterMapper_hpp
+#ifndef Machines_ZX8081_CharacterMapper_hpp
+#define Machines_ZX8081_CharacterMapper_hpp
 
 #include "../Typer.hpp"