diff --git a/ArduPlane/GCS_Mavlink.pde b/ArduPlane/GCS_Mavlink.pde
index d143da8366..33091c0419 100644
--- a/ArduPlane/GCS_Mavlink.pde
+++ b/ArduPlane/GCS_Mavlink.pde
@@ -917,7 +917,7 @@ GCS_MAVLINK::update(void)
 
     if (waypoint_receiving &&
         waypoint_request_i <= waypoint_request_last &&
-        tnow - waypoint_timelast_request > 2000 + (stream_slowdown*20)) {
+        tnow - waypoint_timelast_request > 2000U + (stream_slowdown*20)) {
         waypoint_timelast_request = tnow;
         send_message(MSG_NEXT_WAYPOINT);
     }