diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index a092e17f9631e..30e60bec6c231 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -741,7 +741,9 @@ class AP_InertialSensor : AP_AccelCal_Client
     bool _startup_error_counts_set;
     uint32_t _startup_ms;
 
+#if AP_INERTIALSENSOR_KILL_IMU_ENABLED
     uint8_t imu_kill_mask;
+#endif
 
 #if HAL_INS_TEMPERATURE_CAL_ENABLE
 public:
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
index 79d36134f9496..bef05d69ab01c 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
@@ -164,7 +164,7 @@ void AP_InertialSensor_Backend::_rotate_and_correct_gyro(uint8_t instance, Vecto
  */
 void AP_InertialSensor_Backend::_publish_gyro(uint8_t instance, const Vector3f &gyro) /* front end */
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     _imu._gyro[instance] = gyro;
@@ -263,7 +263,7 @@ void AP_InertialSensor_Backend::_notify_new_gyro_raw_sample(uint8_t instance,
                                                             const Vector3f &gyro,
                                                             uint64_t sample_us)
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     float dt;
@@ -360,7 +360,7 @@ void AP_InertialSensor_Backend::_notify_new_gyro_raw_sample(uint8_t instance,
  */
 void AP_InertialSensor_Backend::_notify_new_delta_angle(uint8_t instance, const Vector3f &dangle)
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     float dt;
@@ -487,7 +487,7 @@ void AP_InertialSensor_Backend::log_gyro_raw(uint8_t instance, const uint64_t sa
  */
 void AP_InertialSensor_Backend::_publish_accel(uint8_t instance, const Vector3f &accel) /* front end */
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     _imu._accel[instance] = accel;
@@ -517,7 +517,7 @@ void AP_InertialSensor_Backend::_notify_new_accel_raw_sample(uint8_t instance,
                                                              uint64_t sample_us,
                                                              bool fsync_set)
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     float dt;
@@ -604,7 +604,7 @@ void AP_InertialSensor_Backend::_notify_new_accel_raw_sample(uint8_t instance,
  */
 void AP_InertialSensor_Backend::_notify_new_delta_velocity(uint8_t instance, const Vector3f &dvel)
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     float dt;
@@ -746,7 +746,7 @@ void AP_InertialSensor_Backend::_inc_gyro_error_count(uint8_t instance)
  */
 void AP_InertialSensor_Backend::_publish_temperature(uint8_t instance, float temperature) /* front end */
 {
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     _imu._temperature[instance] = temperature;
@@ -769,7 +769,7 @@ void AP_InertialSensor_Backend::update_gyro(uint8_t instance) /* front end */
 {    
     WITH_SEMAPHORE(_sem);
 
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     if (_imu._new_gyro_data[instance]) {
@@ -808,7 +808,7 @@ void AP_InertialSensor_Backend::update_accel(uint8_t instance) /* front end */
 {    
     WITH_SEMAPHORE(_sem);
 
-    if ((1U<<instance) & _imu.imu_kill_mask) {
+    if (has_been_killed(instance)) {
         return;
     }
     if (_imu._new_accel_data[instance]) {
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
index b86b9bb57fe15..e70bdaf98c75a 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
@@ -85,6 +85,13 @@ class AP_InertialSensor_Backend
     virtual void handle_external(const AP_ExternalAHRS::ins_data_message_t &pkt) {}
 #endif
 
+#if AP_INERTIALSENSOR_KILL_IMU_ENABLED
+    bool has_been_killed(uint8_t instance) const { return ((1U<<instance) & _imu.imu_kill_mask); }
+#else
+    bool has_been_killed(uint8_t instance) const { return false; }
+#endif
+
+
     /*
       device driver IDs. These are used to fill in the devtype field
       of the device ID, which shows up as INS*ID* parameters to