diff --git a/Tracking/Acts/ActsGeometry/ActsGeometry/ActsExtrapolationTool.h b/Tracking/Acts/ActsGeometry/ActsGeometry/ActsExtrapolationTool.h
index 789be0c33d7bad938bd2647e0e8b00fc373ee889..84830551841f9648fe953d2e18c6c2635e83c34a 100644
--- a/Tracking/Acts/ActsGeometry/ActsGeometry/ActsExtrapolationTool.h
+++ b/Tracking/Acts/ActsGeometry/ActsGeometry/ActsExtrapolationTool.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef ACTSGEOMETRY_ACTSEXTRAPOLATIONTOOL_H
@@ -116,7 +116,7 @@ public:
 
 
 private:
-  std::unique_ptr<ActsExtrapolationDetail::VariantPropagator> m_varProp;
+  std::unique_ptr<const ActsExtrapolationDetail::VariantPropagator> m_varProp;
   std::unique_ptr<const Acts::Logger> m_logger{nullptr};
 
   SG::ReadCondHandleKey<AtlasFieldCacheCondObj> m_fieldCacheCondObjInputKey {this, "AtlasFieldCacheCondObj", "fieldCondObj", "Name of the Magnetic Field conditions object key"};