diff --git a/core/detectors/trd/CbmTrdGeoFactory.cxx b/core/detectors/trd/CbmTrdGeoFactory.cxx
index 827991474cf7e70e6c063112885530268690ef9d..7a0a5b57d260f82b53f7e5023a92aac3c20e7c38 100644
--- a/core/detectors/trd/CbmTrdGeoFactory.cxx
+++ b/core/detectors/trd/CbmTrdGeoFactory.cxx
@@ -499,7 +499,7 @@ InitStatus ChamberBuilder::BackPanel::Init()
   }
   fHeight += hHC;
   // supports for electronics
-  TGeoBBox* faspro_fy = new TGeoBBox("faspro_fy", 1.0 / 2, 0.5 + 0.5 * sizeY, 0.5 * ChamberBuilder::FEB::FASPRO_zspace);
+  TGeoBBox* faspro_fy = new TGeoBBox("faspro_fy", 1.0 / 2, 0.5 * activeAreaY, 0.5 * ChamberBuilder::FEB::FASPRO_zspace);
   TGeoVolume* vol_faspro_fy =
     new TGeoVolume("faspro_fy", faspro_fy, cbm::trd::geo::GetMaterial("TRDG10") /*frameVolMed*/);
   vol_faspro_fy->SetLineColor(kViolet + 2);  // vol_faspro_fy->SetTransparency(50);