diff --git a/src/cb_CTD_Si.cpp b/src/cb_CTD_Si.cpp
index a6a683eb0f4e1aff231e5a672ecd1f17c5f3e755..cd90775124c189a7b4a50946633b099c677ab0d8 100644
--- a/src/cb_CTD_Si.cpp
+++ b/src/cb_CTD_Si.cpp
@@ -48,7 +48,7 @@ static Ref_t createDetector(Detector& desc, xml_h e, SensitiveDetector sens)
 
     if (layerROut[i] > ROut)
       continue; 
-
+    
     string logic_layer_name = detName + _toString(i, "_Logic_lay_%d");
     Volume layerVol(logic_layer_name,Tube(layerRIn[i], layerROut[i], SizeZ / 2.0, 0.0, 360.0 * deg), slice_mat);
     layerVol.setVisAttributes(desc,x_layer.visStr());
@@ -57,7 +57,9 @@ static Ref_t createDetector(Detector& desc, xml_h e, SensitiveDetector sens)
 
     Position     layer_pos = Position(0.0, 0.0, 0.0);
     PlacedVolume layerPV = detVol.placeVolume(layerVol, layer_pos);
+    if (i == 6){i = 20;}
     layerPV.addPhysVolID("layer", i+1);
+    if (i == 20){i = 6;}
   }
 
   DetElement   det(detName, detID);