diff --git a/ArduPlane/GCS_Mavlink.cpp b/ArduPlane/GCS_Mavlink.cpp
index 2cc891dafe..6fe2cc70a9 100644
--- a/ArduPlane/GCS_Mavlink.cpp
+++ b/ArduPlane/GCS_Mavlink.cpp
@@ -804,7 +804,7 @@ MAV_RESULT GCS_MAVLINK_Plane::handle_command_int_do_reposition(const mavlink_com
         return MAV_RESULT_DENIED;
     }
 
-    if (is_zero(packet.param4)) {
+    if (isnan(packet.param4) || is_zero(packet.param4)) {
         requested_position.loiter_ccw = 0;
     } else {
         requested_position.loiter_ccw = 1;