diff --git a/ArduCopter/Copter.h b/ArduCopter/Copter.h
index 9915885060a68..40fb3a320157e 100644
--- a/ArduCopter/Copter.h
+++ b/ArduCopter/Copter.h
@@ -256,7 +256,7 @@ class Copter : public AP_Vehicle {
     AP_SurfaceDistance rangefinder_up_state {ROTATION_PITCH_90, inertial_nav, 1U};
 
     // helper function to get inertially interpolated rangefinder height.
-    bool get_rangefinder_height_interpolated_cm(int32_t& ret) const;
+    bool get_rangefinder_height_interpolated_cm(int32_t& ret);
 
 #if AP_RANGEFINDER_ENABLED
     class SurfaceTracking {
diff --git a/ArduCopter/sensors.cpp b/ArduCopter/sensors.cpp
index f83a1c25e3076..c9b2be574173f 100644
--- a/ArduCopter/sensors.cpp
+++ b/ArduCopter/sensors.cpp
@@ -68,7 +68,7 @@ void Copter::update_rangefinder_terrain_offset()
 }
 
 // helper function to get inertially interpolated rangefinder height.
-bool Copter::get_rangefinder_height_interpolated_cm(int32_t& ret) const
+bool Copter::get_rangefinder_height_interpolated_cm(int32_t& ret)
 {
 #if AP_RANGEFINDER_ENABLED
     return rangefinder_state.get_rangefinder_height_interpolated_cm(ret);