diff --git a/src/BarrelCalorimeter_geo.cpp b/src/BarrelCalorimeter_geo.cpp
index d62e0799e46171c5229bf6354e301a86abab3b83..62b9c6e1f6b0eed769c566b3ab3274a8467e42e5 100644
--- a/src/BarrelCalorimeter_geo.cpp
+++ b/src/BarrelCalorimeter_geo.cpp
@@ -185,7 +185,7 @@ static Ref_t create_detector(Detector& description, xml_h e, SensitiveDetector s
         layer_phv.addPhysVolID("layer", l_num);
         layer.setPlacement(layer_phv);
         // Increment to next layer Z position.
-        double xcut = l_thickness * tan_hphi;
+        double xcut = l_thickness * tan_hphi/2.0;
         l_dim_x += xcut;
         l_pos_z += l_thickness;
         ++l_num;