diff --git a/libraries/AP_Mount/AP_Mount_Backend.cpp b/libraries/AP_Mount/AP_Mount_Backend.cpp
index de48c467c7..80b4215f9d 100644
--- a/libraries/AP_Mount/AP_Mount_Backend.cpp
+++ b/libraries/AP_Mount/AP_Mount_Backend.cpp
@@ -123,7 +123,8 @@ void AP_Mount_Backend::update_targets_from_rc()
 // returns the angle (degrees*100) that the RC_Channel input is receiving
 int32_t AP_Mount_Backend::angle_input(RC_Channel* rc, int16_t angle_min, int16_t angle_max)
 {
-    return (rc->get_reverse() ? -1 : 1) * (rc->radio_in - rc->radio_min) * (int32_t)(angle_max - angle_min) / (rc->radio_max - rc->radio_min) + (rc->get_reverse() ? angle_max : angle_min);
+    return (rc->get_reverse() ? -1 : 1) * (rc->get_radio_in() - rc->get_radio_min()) 
+      * (int32_t)(angle_max - angle_min) / (rc->get_radio_max() - rc->get_radio_min()) + (rc->get_reverse() ? angle_max : angle_min);
 }
 
 // returns the angle (radians) that the RC_Channel input is receiving