diff --git a/sfc/slicer.py b/sfc/slicer.py
index 4c2210c..14c6e49 100755
--- a/sfc/slicer.py
+++ b/sfc/slicer.py
@@ -208,11 +208,11 @@ if height is not None:
 #
 
 if height is not None and height > 0:
-	last_z = height 
+	last_z = height - z_off
 else:
 	last_z = None
 if height is not None and height < 0 and z_levels[-1] > height:
-	z_levels.append(height)
+	z_levels.append(height - z_off)
 	
 for next_z in z_levels:
 	wires = shape.slice(Base.Vector(0, 0, 1), next_z + epsilon)