diff --git a/GeoModelCore/GeoModelKernel/GeoModelKernel/GeoLogVol.h b/GeoModelCore/GeoModelKernel/GeoModelKernel/GeoLogVol.h
index 2a214623383bdeee5d3e6a98235724f14f5fa42a..af7175eaf488eb47091368b6018ed55b714cc51e 100644
--- a/GeoModelCore/GeoModelKernel/GeoModelKernel/GeoLogVol.h
+++ b/GeoModelCore/GeoModelKernel/GeoModelKernel/GeoLogVol.h
@@ -35,6 +35,7 @@ class GeoLogVol : public RCBase
   
   //	Returns the material of the logical volume.
   const GeoMaterial* getMaterial () const {
+     std::shared_lock lock{m_mutex};
      return m_material;
   }