diff --git a/mapper.c b/mapper.c
index 6753de1..4422b7f 100644
--- a/mapper.c
+++ b/mapper.c
@@ -1,3 +1,11 @@
+/*
+ * gbsplay is a Gameboy sound player
+ *
+ * 2020-2022 (C) by Tobias Diedrich <ranma+gbsplay@tdiedrich.de>
+ *
+ * Licensed under GNU GPL v1 or, at your option, any later version.
+ */
+
 #include <stdlib.h>
 #include <assert.h>