diff --git a/src/components/ConcernementMapItem.vue b/src/components/ConcernementMapItem.vue
index f0001e5..d2c45b8 100644
--- a/src/components/ConcernementMapItem.vue
+++ b/src/components/ConcernementMapItem.vue
@@ -195,27 +195,26 @@ export default {
           this.handlePaperVisibilityOnMapMode()
         }
         if(this.mapitem.clone){
-          let state = false;
+          let is_visible = false;
           if(n === 'superposition'){
             // superposition mapemode all clones are visible
-            state = true;
+            is_visible = true;
           }else{
             if(this.opened_concernement){
               if(this.mapitem.is_open){
-                state = true;
+                is_visible = true;
               }else{
+                // keep open the clones that are superposed to the opend map_item
                 let opened_mapitem_id = this.opened_concernement.opened_mapitem_id;
-                if(this.opened_concernement.superposed_mapitem_id_by_mapitem_id[opened_mapitem_id].indexOf(this.mapitem.id) !== -1){
-                  state = true;
+                if (this.opened_concernement.superposed_mapitem_id_by_mapitem_id && this.opened_concernement.superposed_mapitem_id_by_mapitem_id[opened_mapitem_id]) {
+                  if(this.opened_concernement.superposed_mapitem_id_by_mapitem_id[opened_mapitem_id].indexOf(this.mapitem.id) !== -1){
+                    is_visible = true;
+                  }
                 }
               }
             }
           }
-          if(state){
-            this.handleMapitemVisibility(true);
-          }else{
-            this.handleMapitemVisibility(false);
-          }
+          this.handleMapitemVisibility(is_visible);
         }
       },
       deep: true