diff --git a/src/viewer.cpp b/src/viewer.cpp
index 309095c09029ed6f5cca82b078716e3ff8435d6f..423f9efe9082f54b6a20c41703f07b968e068737 100644
--- a/src/viewer.cpp
+++ b/src/viewer.cpp
@@ -386,7 +386,7 @@ void Volusion::displayMO()
         if(val_comboEdge==0)
         {
 
-            for(auto vect : simul.aiguille->belonging_cells)
+            for(const auto& vect : simul.aiguille->belonging_cells)
             {
 //                 m_topo_render->overdrawDart(simul.aiguille->parts_[i]->d,10.0f,1.0f,0,0);
                 for(Dart it : vect)
@@ -428,7 +428,7 @@ void Volusion::displayMO()
         m_topo_render->updateData(simul.envMap_.map, simul.envMap_.position,  0.8f, 0.8f, 0.8f);
         if(val_comboEdge==0)
         {
-            for(auto vect : simul.aiguille->neighbor_cells)
+            for(const auto& vect : simul.aiguille->neighbor_cells)
             {
 //                 m_topo_render->overdrawDart(simul.aiguille->parts_[i]->d,10.0f,1.0f,0,0);
                 for(Dart it : vect)
@@ -552,7 +552,7 @@ void Volusion::displayObj()
         for (ArticulatedObject * o : simul.objects)
         {
             CGoGNout<<" size belong :"<< o->belonging_cells.size()<< " || nbseg :"<<o->nbEdges << CGoGNendl;
-            for(auto vect : o->belonging_cells)
+            for(const auto& vect : o->belonging_cells)
             {
             CGoGNout<<" size vector :"<< vect.size() << CGoGNendl;
     //                 m_topo_render->overdrawDart(simul.aiguille->parts_[i]->d,10.0f,1.0f,0,0);
@@ -592,7 +592,7 @@ void Volusion::displayObj()
         m_topo_render->updateData(simul.envMap_.map, simul.envMap_.position,  0.8f, 0.8f, 0.8f);
         for (ArticulatedObject * o : simul.objects)
         {
-            for(auto vect : o->neighbor_cells)
+            for(const auto& vect : o->neighbor_cells)
             {
     //                 m_topo_render->overdrawDart(simul.aiguille->parts_[i]->d,10.0f,1.0f,0,0);
                 for(Dart it : vect)