diff --git a/boards/px4/fmu-v5x/src/board_config.h b/boards/px4/fmu-v5x/src/board_config.h
index 770a984945f..afea105c199 100644
--- a/boards/px4/fmu-v5x/src/board_config.h
+++ b/boards/px4/fmu-v5x/src/board_config.h
@@ -116,6 +116,8 @@
 #define GPIO_I2C4_DRDY1_BMP388      /* PG5  */  (GPIO_INPUT|GPIO_FLOAT|GPIO_EXTI|GPIO_PORTG|GPIO_PIN5)
 #define GPIO_PG6                    /* PG6  */  (GPIO_INPUT|GPIO_PULLUP|GPIO_PORTG|GPIO_PIN6)
 
+#define PX4_I2C_BUS_MTD 4
+
 /*
  * ADC channels
  *