diff --git a/Geometry/MTDCommonData/src/BTLNumberingScheme.cc b/Geometry/MTDCommonData/src/BTLNumberingScheme.cc
index 58e013830b044..253f974b5fd03 100644
--- a/Geometry/MTDCommonData/src/BTLNumberingScheme.cc
+++ b/Geometry/MTDCommonData/src/BTLNumberingScheme.cc
@@ -117,7 +117,11 @@ uint32_t BTLNumberingScheme::getUnitID(const MTDBaseNumber& baseNumber) const {
         modCopy = negModCopy[modCopy - 1];
       }
 
-      bool isV2(baseNumber.getLevelName(0).back() != 'l');
+      bool isV2(bareBaseName(baseNumber.getLevelName(0)).back() != 'l');
+
+#ifdef EDM_ML_DEBUG
+      LogDebug("MTDGeom") << "BTLNumberingScheme::getUnitID(): isV2 " << isV2;
+#endif
 
       if (isV2) {
         // V2: the type is embedded in crystal name