diff --git a/geometry/upstream/sieve.gdml b/geometry/upstream/sieve.gdml
index 0cc799303..eb9358789 100644
--- a/geometry/upstream/sieve.gdml
+++ b/geometry/upstream/sieve.gdml
@@ -104,7 +104,7 @@
   <tube name="sieve_hole_solid"
     rmin="0."
     rmax="sieve_hole_diameter/2"
-    z="sieve_system_thickness+2"
+    z="sieve_system_thickness"
     startphi="0" deltaphi="360.0" aunit="deg"
     />