diff --git a/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.cpp b/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.cpp
index c4b6adb74d..be1a01351f 100644
--- a/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.cpp
+++ b/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.cpp
@@ -312,7 +312,7 @@ void AC_AttitudeControl_Heli::passthrough_bf_roll_pitch_rate_yaw(float roll_pass
 
     // add desired target to yaw
     _ang_vel_body.z += _ang_vel_target.z;
-    _thrust_error_angle = norm(_att_error_rot_vec_rad.x, _att_error_rot_vec_rad.y);
+    _thrust_error_angle = _att_error_rot_vec_rad.xy().length();
 }
 
 void AC_AttitudeControl_Heli::integrate_bf_rate_error_to_angle_errors()