diff --git a/ContainerShip/ContainerShip/FormMapWithSetShips.cs b/ContainerShip/ContainerShip/FormMapWithSetShips.cs
index 52785df..42c141b 100644
--- a/ContainerShip/ContainerShip/FormMapWithSetShips.cs
+++ b/ContainerShip/ContainerShip/FormMapWithSetShips.cs
@@ -46,9 +46,9 @@ namespace ContainerShip
             int index = listBoxMaps.SelectedIndex;
 
             listBoxMaps.Items.Clear();
-            foreach (string key in _mapsCollection.Keys)
+            for (int i = 0; i < _mapsCollection.Keys.Count; i++)
             {
-                listBoxMaps.Items.Add(key);
+                listBoxMaps.Items.Add(_mapsCollection.Keys[i]);
             }
 
             if (listBoxMaps.Items.Count > 0 && (index == -1 || index >= listBoxMaps.Items.Count))