diff --git a/sw/airborne/mcu.c b/sw/airborne/mcu.c
index c0472a7d59..1757c1f889 100644
--- a/sw/airborne/mcu.c
+++ b/sw/airborne/mcu.c
@@ -101,6 +101,9 @@ void mcu_init(void) {
 #ifdef USE_I2C2
   i2c2_init();
 #endif
+#ifdef USE_I2C3
+  i2c3_init();
+#endif
 #ifdef USE_ADC
   adc_init();
 #endif