diff --git a/ArduPlane/quadplane.cpp b/ArduPlane/quadplane.cpp
index 42f7c734fb..3995f6e4b2 100644
--- a/ArduPlane/quadplane.cpp
+++ b/ArduPlane/quadplane.cpp
@@ -446,7 +446,7 @@ QuadPlane::QuadPlane(AP_AHRS_NavEKF &_ahrs) :
 void QuadPlane::setup_default_channels(uint8_t num_motors)
 {
     for (uint8_t i=0; i<num_motors; i++) {
-        SRV_Channels::set_aux_channel_default((SRV_Channel::Aux_servo_function_t)(SRV_Channel::k_motor1+i), CH_5+i);
+        SRV_Channels::set_aux_channel_default(SRV_Channels::get_motor_function(i), CH_5+i);
     }
 }
     
@@ -595,7 +595,7 @@ bool QuadPlane::setup(void)
     // setup the trim of any motors used by AP_Motors so px4io
     // failsafe will disable motors
     for (uint8_t i=0; i<8; i++) {
-        SRV_Channel::Aux_servo_function_t func = (SRV_Channel::Aux_servo_function_t)(SRV_Channel::k_motor1+i);
+        SRV_Channel::Aux_servo_function_t func = SRV_Channels::get_motor_function(i);
         SRV_Channels::set_failsafe_pwm(func, thr_min_pwm);
     }