diff --git a/code/modules/overmap/ships/ship.dm b/code/modules/overmap/ships/ship.dm
index b080c41b07..3397fe9a76 100644
--- a/code/modules/overmap/ships/ship.dm
+++ b/code/modules/overmap/ships/ship.dm
@@ -72,6 +72,7 @@
 		return INFINITY
 	return max(abs(speed[1]),abs(speed[2]))/get_acceleration()
 
+#define SIGN(X) (X == 0 ? 0 : (X > 0 ? 1 : -1))
 /obj/effect/map/ship/proc/decelerate()
 	if(!is_still() && can_burn())
 		if (speed[1])