diff --git a/Machines/Acorn/Archimedes/Keyboard.hpp b/Machines/Acorn/Archimedes/Keyboard.hpp
index 5eb5e8aebf..e99a4c06a4 100644
--- a/Machines/Acorn/Archimedes/Keyboard.hpp
+++ b/Machines/Acorn/Archimedes/Keyboard.hpp
@@ -213,7 +213,7 @@ struct Keyboard {
 			return 3;
 		}
 
-		virtual void set_button_pressed(int index, bool is_pressed) {
+		virtual void set_button_pressed(int index, bool is_pressed) override {
 			keyboard_.set_key_state(7, index, is_pressed);
 		}