diff --git a/libraries/AP_Common/Location.cpp b/libraries/AP_Common/Location.cpp
index 0280ee3869..083016c557 100644
--- a/libraries/AP_Common/Location.cpp
+++ b/libraries/AP_Common/Location.cpp
@@ -103,7 +103,7 @@ Location::AltFrame Location::get_alt_frame() const
 bool Location::get_alt_cm(AltFrame desired_frame, int32_t &ret_alt_cm) const
 {
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-    if (lat == 0 && lng == 0) {
+    if (!initialised()) {
         AP_HAL::panic("Should not be called on invalid location");
     }
 #endif
diff --git a/libraries/AP_Common/Location.h b/libraries/AP_Common/Location.h
index 6cea7b369f..a881e0e541 100644
--- a/libraries/AP_Common/Location.h
+++ b/libraries/AP_Common/Location.h
@@ -112,6 +112,8 @@ public:
      */
     float line_path_proportion(const Location &point1, const Location &point2) const;
 
+    bool initialised() const { return (lat !=0 || lng != 0); }
+
 private:
     static AP_Terrain *_terrain;