diff --git a/src/arch/msp430fr5969lp/driver/i2c.cc b/src/arch/msp430fr5969lp/driver/i2c.cc
index be41a50f7d5d1d50225320a97f7f36dcd2ce9fa0..0e0c376010d6bf014812351223d5bce4948889c3 100644
--- a/src/arch/msp430fr5969lp/driver/i2c.cc
+++ b/src/arch/msp430fr5969lp/driver/i2c.cc
@@ -2,6 +2,10 @@
 #include "arch.h"
 #include <msp430.h>
 
+#ifndef F_I2C
+#define F_I2C 100000
+#endif
+
 volatile unsigned short old_ifg = 0;
 
 signed char I2C::setup()