diff --git a/Phys/DaVinci/python/DaVinci/Configuration.py b/Phys/DaVinci/python/DaVinci/Configuration.py
index 9a748a7caefb6f7b7904c772338f26377c9f8386..fb3bf6c9143b5ebce51ac4b17c1f4f7f84fcbf2f 100644
--- a/Phys/DaVinci/python/DaVinci/Configuration.py
+++ b/Phys/DaVinci/python/DaVinci/Configuration.py
@@ -596,7 +596,7 @@ class DaVinci(LHCbConfigurableUser) :
                 log.info ('Define CondDB( Upgrade = True ) ')
                 _db.Upgrade = True
             if  not self.isPropertySet('Detectors') or not self.getProp('Detectors') :
-                upgrade_only_dets = [ d for d in __known_upgrade_detectors__ if d not in __known_default_detectors]
+                upgrade_only_dets = [ d for d in self.__known_upgrade_detectors__ if d not in self.__known_default_detectors]
                 log.warning("It is suspicious that the list of ``Detectors'' is not specified though ``DataType=Upgrade'' ...")
                 log.warning("Sure that none of the upgrade-only detectors %s are to be specified via ``Detectors''?" % upgrade_only_dets )
             from Configurables import SimConf