diff --git a/Pr/PrKernel/include/PrKernel/PrFTZoneHandler.h b/Pr/PrKernel/include/PrKernel/PrFTZoneHandler.h
index a6e5b2d6e96b450a9ad9143644dce9ac7d5c58d2..8d3762c535f184bfc2bc66d6bf6991c43a3ab2ab 100644
--- a/Pr/PrKernel/include/PrKernel/PrFTZoneHandler.h
+++ b/Pr/PrKernel/include/PrKernel/PrFTZoneHandler.h
@@ -33,7 +33,11 @@ namespace FTZoneCache {
     PrFTZoneHandler( DeFT const& ftDet ) {
 #ifdef USE_DD4HEP
       auto func = [this]( const DeFTLayer& layer ) {
-        const auto id = layer.layerID();
+        // NOT FOR MERGE
+        // In DetDesc Ids number from 0, but with DD4HEP seem to start at 4 .... ??
+        // This should be fixed at source in Detector but for now just correct here.
+        const auto id = layer.layerID() - 4;
+        // NOT FOR MERGE
         // fixme
         DetectorSegment seg( 0, layer.globalZ(), layer.dxdy(), layer.dzdy(), 0., 0. );
         const auto      xmax = 0.5f * layer.sizeX();