diff --git a/src/gruvin9x/rtc.cpp b/src/gruvin9x/rtc.cpp
index 1c0261164..a85e0c86f 100644
--- a/src/gruvin9x/rtc.cpp
+++ b/src/gruvin9x/rtc.cpp
@@ -36,6 +36,7 @@
 /*  RTC controls                                                            */
 
 #include "../open9x.h"
+#include "rtc.h"
 
 #define SCL_LOW()	DDRD |=	0x01		/* SCL = LOW */
 #define SCL_HIGH()	DDRD &=	~0x01		/* SCL = High-Z */