diff --git a/libraries/AC_Avoidance/AC_Avoid.h b/libraries/AC_Avoidance/AC_Avoid.h
index 933cfdacbe..b61521b2b4 100644
--- a/libraries/AC_Avoidance/AC_Avoid.h
+++ b/libraries/AC_Avoidance/AC_Avoid.h
@@ -81,7 +81,7 @@ public:
 
     // enable/disable proximity based avoidance
     void proximity_avoidance_enable(bool on_off) { _proximity_enabled = on_off; }
-    bool proximity_avoidance_enabled() { return _proximity_enabled; }
+    bool proximity_avoidance_enabled() const { return _proximity_enabled; }
 
     // helper functions