diff --git a/src/simulation/Simulation.cpp b/src/simulation/Simulation.cpp
index 660c7238b..f25a12487 100644
--- a/src/simulation/Simulation.cpp
+++ b/src/simulation/Simulation.cpp
@@ -819,7 +819,7 @@ void *Simulation::transform_save(void *odata, int *size, matrix2d transform, vec
 			pos = v2d_add(m2d_multiply_v2d(transform,pos),translate);
 			nx = pos.x/CELL;
 			ny = pos.y/CELL;
-			if (nx<0 || nx>=nw || ny<0 || ny>=nh)
+			if (nx<0 || nx>=nw/CELL || ny<0 || ny>=nh/CELL)
 				continue;
 			if (bmapo[y][x])
 			{