diff --git a/src/cam.c b/src/cam.c
index 1946d50..805478a 100644
--- a/src/cam.c
+++ b/src/cam.c
@@ -680,8 +680,9 @@ int lightship_check() {
             itss_space_get();
 
             // Check heading delta > 4º
-            int diff = ((epv.space.heading - lightship->last_pos.heading) + 180) % 360 - 180;
-            if (diff > 40) rv = 1;
+            int diff = epv.space.heading - lightship->last_pos.heading;
+            diff += (diff > 180) ? -360 : (diff < -180) ? 360 : 0;
+            if (abs(diff) > 40) rv = 1;
 
             if (!rv) {
                 // Check speed delta > 0.5 m/s