diff --git a/twi-lowlevel.h b/twi-lowlevel.h
index 72609be..1619272 100644
--- a/twi-lowlevel.h
+++ b/twi-lowlevel.h
@@ -22,7 +22,7 @@
 
 #include <inttypes.h>
 
-#include "../clock.h"
+#include "../clock.hpp"
 
 //#define ATMEGA8