diff --git a/libraries/AP_HAL_Linux/GPIO_Bebop.cpp b/libraries/AP_HAL_Linux/GPIO_Bebop.cpp
index 58f7cf6ca1..3790e0cbe2 100644
--- a/libraries/AP_HAL_Linux/GPIO_Bebop.cpp
+++ b/libraries/AP_HAL_Linux/GPIO_Bebop.cpp
@@ -1,8 +1,7 @@
 #include <AP_Common/AP_Common.h>
 
-#include "GPIO_Bebop.h"
-
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP
+#include "GPIO_Bebop.h"
 
 const unsigned Linux::GPIO_Sysfs::pin_table[] = {
     [BEBOP_GPIO_CAMV_NRST] = 129,
diff --git a/libraries/AP_HAL_Linux/GPIO_Disco.cpp b/libraries/AP_HAL_Linux/GPIO_Disco.cpp
index 1766f234b8..2c797e843f 100644
--- a/libraries/AP_HAL_Linux/GPIO_Disco.cpp
+++ b/libraries/AP_HAL_Linux/GPIO_Disco.cpp
@@ -1,11 +1,12 @@
 #include <AP_Common/AP_Common.h>
 
-#include "GPIO_Disco.h"
-
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DISCO
 
+#include "GPIO_Disco.h"
+
 const unsigned Linux::GPIO_Sysfs::pin_table[] = {
     [DISCO_GPIO_MPU6050_DRDY] = 91,
+    [LINUX_GPIO_ULTRASOUND_VOLTAGE] = 200,
 };
 
 const uint8_t Linux::GPIO_Sysfs::n_pins = _DISCO_GPIO_MAX;
diff --git a/libraries/AP_HAL_Linux/GPIO_Disco.h b/libraries/AP_HAL_Linux/GPIO_Disco.h
index b9b34937b0..4d55d5e932 100644
--- a/libraries/AP_HAL_Linux/GPIO_Disco.h
+++ b/libraries/AP_HAL_Linux/GPIO_Disco.h
@@ -4,5 +4,6 @@
 
 enum gpio_disco {
     DISCO_GPIO_MPU6050_DRDY,
+    LINUX_GPIO_ULTRASOUND_VOLTAGE,
     _DISCO_GPIO_MAX,
 };