From e7dec69f0ad709dc7e6e5799c5998e571f03681e Mon Sep 17 00:00:00 2001
From: Matthias Wirth <matthias.wirth@gmail.com>
Date: Thu, 17 Oct 2024 16:32:01 +0200
Subject: [PATCH] speed_check: decrement speedUnreliable speed is unknown

---
 track.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/track.c b/track.c
index 731f1a99..7f82b36d 100644
--- a/track.c
+++ b/track.c
@@ -598,7 +598,9 @@ static int speed_check(struct aircraft *a, datasource_t source, double lat, doub
         range += 250;
     }
 
-    if (distance > 2.5f && (track_diff < 70 || track_diff == -1)) {
+    if (transmitted_speed < 0) {
+            mm->speedUnreliable = -1;
+    } else if (distance > 2.5f && (track_diff < 70 || track_diff == -1)) {
         if (distance <= range + (((float) elapsed + 50.0f) * (1.0f / 1000.0f)) * (transmitted_speed * knots_to_meterpersecond)) {
             mm->speedUnreliable = -1;
         } else if (distance > range + (((float) elapsed + 400.0f) * (1.0f / 1000.0f)) * (transmitted_speed * knots_to_meterpersecond)) {