diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index e983491134..b19b2614ad 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -2133,11 +2133,7 @@ bool AP_InertialSensor::get_fixed_mount_accel_cal_sample(uint8_t sample_num, Vec
         return false;
     }
     _accel_calibrator[_acc_body_aligned-1].get_sample_corrected(sample_num, ret);
-    if (_board_orientation == ROTATION_CUSTOM && _custom_rotation) {
-        ret = *_custom_rotation * ret;
-    } else {
-        ret.rotate(_board_orientation);
-    }
+    ret.rotate(_board_orientation);
     return true;
 }
 
@@ -2162,11 +2158,7 @@ bool AP_InertialSensor::get_primary_accel_cal_sample_avg(uint8_t sample_num, Vec
     }
     avg /= count;
     ret = avg;
-    if (_board_orientation == ROTATION_CUSTOM && _custom_rotation) {
-        ret = *_custom_rotation * ret;
-    } else {
-        ret.rotate(_board_orientation);
-    }
+    ret.rotate(_board_orientation);
     return true;
 }
 
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index f4618664fc..fbbceff9da 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -224,9 +224,8 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
     // set overall board orientation
-    void set_board_orientation(enum Rotation orientation, Matrix3f* custom_rotation = nullptr) {
+    void set_board_orientation(enum Rotation orientation) {
         _board_orientation = orientation;
-        _custom_rotation = custom_rotation;
     }
 
     // return the selected loop rate at which samples are made avilable
@@ -595,7 +594,6 @@ private:
     
     // board orientation from AHRS
     enum Rotation _board_orientation;
-    Matrix3f* _custom_rotation;
 
     // per-sensor orientation to allow for board type defaults at runtime
     enum Rotation _gyro_orientation[INS_MAX_INSTANCES];
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
index e0c8dc21ad..4177f9d4e9 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
@@ -126,11 +126,7 @@ void AP_InertialSensor_Backend::_rotate_and_correct_accel(uint8_t instance, Vect
     }
 
     // rotate to body frame
-    if (_imu._board_orientation == ROTATION_CUSTOM && _imu._custom_rotation) {
-        accel = *_imu._custom_rotation * accel;
-    } else {
-        accel.rotate(_imu._board_orientation);
-    }
+    accel.rotate(_imu._board_orientation);
 }
 
 void AP_InertialSensor_Backend::_rotate_and_correct_gyro(uint8_t instance, Vector3f &gyro) 
@@ -155,11 +151,7 @@ void AP_InertialSensor_Backend::_rotate_and_correct_gyro(uint8_t instance, Vecto
         gyro -= _imu._gyro_offset[instance];
     }
 
-    if (_imu._board_orientation == ROTATION_CUSTOM && _imu._custom_rotation) {
-        gyro = *_imu._custom_rotation * gyro;
-    } else {
-        gyro.rotate(_imu._board_orientation);
-    }
+    gyro.rotate(_imu._board_orientation);
 }
 
 /*