diff --git a/twi-lowlevel.cpp b/twi-lowlevel.cpp
index aa051d7..c50f3b5 100644
--- a/twi-lowlevel.cpp
+++ b/twi-lowlevel.cpp
@@ -79,7 +79,7 @@ void twi_init(void)
   // initialize twi prescaler and bit rate
   cbi(TWSR, TWPS0);
   cbi(TWSR, TWPS1);
-  TWBR = ((CPU_FREQ / TWI_FREQ) - 16) / 2;
+  TWBR = ((F_CPU / TWI_FREQ) - 16) / 2;
 
   /* twi bit rate formula from atmega128 manual pg 204
   SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
diff --git a/twi-lowlevel.h b/twi-lowlevel.h
index d898f01..72609be 100644
--- a/twi-lowlevel.h
+++ b/twi-lowlevel.h
@@ -22,11 +22,9 @@
 
 #include <inttypes.h>
 
-//#define ATMEGA8
+#include "../clock.h"
 
-#ifndef CPU_FREQ
-#define CPU_FREQ 16000000L
-#endif
+//#define ATMEGA8
 
 #ifndef TWI_FREQ
 #define TWI_FREQ 100000L