diff --git a/libraries/AC_WPNav/AC_WPNav.h b/libraries/AC_WPNav/AC_WPNav.h
index 158f6f7976..4a4432aff8 100644
--- a/libraries/AC_WPNav/AC_WPNav.h
+++ b/libraries/AC_WPNav/AC_WPNav.h
@@ -140,6 +140,7 @@ public:
         return get_wp_distance_to_destination() < _wp_radius_cm;
     }
 
+    // get wp_radius parameter value in cm
     float get_wp_radius_cm() const { return _wp_radius_cm; }
 
     /// update_wpnav - run the wp controller - should be called at 100hz or higher