Fixed typo.
diff --git a/contiki/conf/clock-conf.h.example b/contiki/conf/clock-conf.h.example
index a3797e3..a690e15 100644
--- a/contiki/conf/clock-conf.h.example
+++ b/contiki/conf/clock-conf.h.example
@@ -1,5 +1,5 @@
 #ifndef __CLOCK_CONF_H__
-#define __CLOCK_CONF_H___
+#define __CLOCK_CONF_H__
 
 typedef unsigned short clock_time_t;