diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index 9a91f35a16..7694850181 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -99,8 +99,7 @@
 
 #include "modules/dataman/dataman.h"
 
-extern device::Device *PX4IO_i2c_interface() weak_function;
-extern device::Device *PX4IO_serial_interface() weak_function;
+#include "px4io_driver.h"
 
 #define PX4IO_SET_DEBUG			_IOC(0xff00, 0)
 #define PX4IO_INAIR_RESTART_ENABLE	_IOC(0xff00, 1)
@@ -2973,10 +2972,12 @@ get_interface()
 
 #ifndef CONFIG_ARCH_BOARD_PX4FMU_V1
 
+#ifdef PX4IO_SERIAL_BASE
 	/* try for a serial interface */
 	if (PX4IO_serial_interface != nullptr) {
 		interface = PX4IO_serial_interface();
 	}
+#endif
 
 	if (interface != nullptr) {
 		goto got;
@@ -2984,10 +2985,12 @@ get_interface()
 
 #endif
 
+#ifdef PX4_I2C_OBDEV_PX4IO
 	/* try for an I2C interface if we haven't got a serial one */
 	if (PX4IO_i2c_interface != nullptr) {
 		interface = PX4IO_i2c_interface();
 	}
+#endif
 
 	if (interface != nullptr) {
 		goto got;
diff --git a/src/drivers/px4io/px4io_driver.h b/src/drivers/px4io/px4io_driver.h
index 0944412fb0..591c3920d2 100644
--- a/src/drivers/px4io/px4io_driver.h
+++ b/src/drivers/px4io/px4io_driver.h
@@ -39,6 +39,8 @@
 
 #pragma once
 
+#include <board_config.h>
+
 #ifdef PX4_I2C_OBDEV_PX4IO
 device::Device	*PX4IO_i2c_interface();
 #endif
diff --git a/src/drivers/px4io/px4io_i2c.cpp b/src/drivers/px4io/px4io_i2c.cpp
index 574a58f52a..4574ec732a 100755
--- a/src/drivers/px4io/px4io_i2c.cpp
+++ b/src/drivers/px4io/px4io_i2c.cpp
@@ -53,9 +53,9 @@
 
 #include <drivers/device/i2c.h>
 
-#ifdef PX4_I2C_OBDEV_PX4IO
+#include "px4io_driver.h"
 
-device::Device	*PX4IO_i2c_interface();
+#ifdef PX4_I2C_OBDEV_PX4IO
 
 class PX4IO_I2C : public device::I2C
 {
diff --git a/src/drivers/px4io/px4io_serial.cpp b/src/drivers/px4io/px4io_serial.cpp
index 93f55f9486..c05883aeb8 100644
--- a/src/drivers/px4io/px4io_serial.cpp
+++ b/src/drivers/px4io/px4io_serial.cpp
@@ -68,9 +68,9 @@
 
 #include <modules/px4iofirmware/protocol.h>
 
-#ifdef PX4IO_SERIAL_BASE
+#include "px4io_driver.h"
 
-device::Device	*PX4IO_serial_interface();
+#ifdef PX4IO_SERIAL_BASE
 
 /* serial register accessors */
 #define REG(_x)		(*(volatile uint32_t *)(PX4IO_SERIAL_BASE + _x))