diff --git a/aliby/tile/tiler.py b/aliby/tile/tiler.py
index d8f9bac2bda94e330041c13cb600afa6b0581168..1c271d919db85b4f1c8fc3606df4361d98762af5 100644
--- a/aliby/tile/tiler.py
+++ b/aliby/tile/tiler.py
@@ -135,7 +135,7 @@ class TrapLocations:
         self.max_size = max_size
         self.initial_location = initial_location
         self.traps = [
-            Trap(centre, self, tile_size, max_size)
+            Trap(centre, self, tile_size or max_size, max_size)
             for centre in initial_location
         ]
         self.drifts = drifts