diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index 1e48a6e997..6fe7dd29a6 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -1790,7 +1790,7 @@ bool AP_InertialSensor::get_primary_accel_cal_sample_avg(uint8_t sample_num, Vec
 /*
   perform a simple 1D accel calibration, returning mavlink result code
  */
-uint8_t AP_InertialSensor::simple_accel_cal(AP_AHRS &ahrs)
+MAV_RESULT AP_InertialSensor::simple_accel_cal(AP_AHRS &ahrs)
 {
     uint8_t num_accels = MIN(get_accel_count(), INS_MAX_INSTANCES);
     Vector3f last_average[INS_MAX_INSTANCES];
@@ -1894,7 +1894,7 @@ uint8_t AP_InertialSensor::simple_accel_cal(AP_AHRS &ahrs)
         }
     }
 
-    uint8_t result = MAV_RESULT_ACCEPTED;
+    MAV_RESULT result = MAV_RESULT_ACCEPTED;
 
     // see if we've passed
     for (uint8_t k=0; k<num_accels; k++) {
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index 07b68f6712..f02c97626b 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -270,8 +270,8 @@ public:
     void acal_update();
 
     // simple accel calibration
-    uint8_t simple_accel_cal(AP_AHRS &ahrs);
-    
+    MAV_RESULT simple_accel_cal(AP_AHRS &ahrs);
+
     bool accel_cal_requires_reboot() const { return _accel_cal_requires_reboot; }
 
     // return time in microseconds of last update() call