diff --git a/dev/cc2420/cc2420.c b/dev/cc2420/cc2420.c
index d455e02df..7c7c97461 100644
--- a/dev/cc2420/cc2420.c
+++ b/dev/cc2420/cc2420.c
@@ -497,7 +497,7 @@ init_security(void)
 }
 /*---------------------------------------------------------------------------*/
 static void
-set_key(uint8_t *key)
+set_key(const uint8_t *key)
 {
   GET_LOCK();