diff --git a/modules/mol/base/src/impl/entity_impl.cc b/modules/mol/base/src/impl/entity_impl.cc
index 937a63213164791056f34434b5c69267f8dc1047..2eeaf86cd6d116c797feb902284a8119f9171806 100644
--- a/modules/mol/base/src/impl/entity_impl.cc
+++ b/modules/mol/base/src/impl/entity_impl.cc
@@ -812,8 +812,9 @@ TorsionImplP EntityImpl::FindTorsion(const AtomImplPtr& a1,
   return TorsionImplP();
 }
 
-AtomImplList EntityImpl::FindWithin(const geom::Vec3& pos, Real radius) const
+AtomImplList EntityImpl::FindWithin(const geom::Vec3& pos, Real radius)
 {
+  this->UpdateOrganizerIfNeeded();
   SpatialAtomOrganizer::ItemList alist = atom_organizer_.FindWithin(pos,radius);
   return alist;
 }
diff --git a/modules/mol/base/src/impl/entity_impl.hh b/modules/mol/base/src/impl/entity_impl.hh
index 5033bd55e806f4cb21331649a663ac36ef28fe7f..7a1e3a30309371f1a921fa6ba598f618335b9e62 100644
--- a/modules/mol/base/src/impl/entity_impl.hh
+++ b/modules/mol/base/src/impl/entity_impl.hh
@@ -160,7 +160,7 @@ public:
   
   void UpdateOrganizer();
   
-  AtomImplList FindWithin(const geom::Vec3& pos, Real radius) const;
+  AtomImplList FindWithin(const geom::Vec3& pos, Real radius);
   // use query flag defaults
   EntityView Select(const EntityHandle& h, const Query& q) const;
   // override query flag defaults with given flags