diff --git a/include/c64/kernalio.h b/include/c64/kernalio.h
index 6a7f469..8d94d2b 100644
--- a/include/c64/kernalio.h
+++ b/include/c64/kernalio.h
@@ -1,5 +1,5 @@
-
 #ifndef C64_KERNALIO_H
+#define C64_KERNALIO_H
 
 // Error and status codes returned by krnio_status