Fixed typo.
diff --git a/contiki-apple2/conf/clock-conf.h b/contiki-apple2/conf/clock-conf.h
index 18dc221..40f7b49 100644
--- a/contiki-apple2/conf/clock-conf.h
+++ b/contiki-apple2/conf/clock-conf.h
@@ -1,5 +1,5 @@
 #ifndef __CLOCK_CONF_H__
-#define __CLOCK_CONF_H___
+#define __CLOCK_CONF_H__
 
 typedef unsigned short clock_time_t;