diff --git a/Detector/DetSegmentation/DetSegmentation/GridDriftChamber.h b/Detector/DetSegmentation/DetSegmentation/GridDriftChamber.h
index 2a8631ce79edfc54030d5f77dd5a117e79dfda7d..82a4e8f041b4a9934977fb4943b69a782fc4b37e 100644
--- a/Detector/DetSegmentation/DetSegmentation/GridDriftChamber.h
+++ b/Detector/DetSegmentation/DetSegmentation/GridDriftChamber.h
@@ -69,7 +69,7 @@ public:
     updateParams(layer);
     for (int i = 0; i<numWires; ++i) {
 
-      auto phi_start = _currentLayerphi * (i+0.5) + phi0;
+      auto phi_start = _currentLayerphi * (i+0.5) + m_offset;
       auto phi_end = phi_start + _currentLayerphi;
 
       TVector3 Wstart = returnWirePosition(phi_start, 1);