diff --git a/code/game/turfs/simulated/floor/plating/asteroid.dm b/code/game/turfs/simulated/floor/plating/asteroid.dm
index 848a7e8219..2649a3a14d 100644
--- a/code/game/turfs/simulated/floor/plating/asteroid.dm
+++ b/code/game/turfs/simulated/floor/plating/asteroid.dm
@@ -193,7 +193,7 @@
 
 		var/list/L = list(45)
 		if(IsOdd(dir2angle(dir))) // We're going at an angle and we want thick angled tunnels.
-			L -= 45
+			L += -45
 
 		// Expand the edges of our tunnel
 		for(var/edge_angle in L)