diff --git a/OSM_Regions/Converter.cs b/OSM_Regions/Converter.cs
index 6818504..8d5abb7 100644
--- a/OSM_Regions/Converter.cs
+++ b/OSM_Regions/Converter.cs
@@ -168,8 +168,8 @@ public class Converter(float regionSize, string? exportFolderPath = null, ILogge
         int count = 0;
         DateTime print = DateTime.Now;
         DateTime start = DateTime.Now;
-        List<ulong> wayIds = new();
-        List<ulong> nodeIds = new();
+        HashSet<ulong> wayIds = new();
+        HashSet<ulong> nodeIds = new();
         foreach (string path in wayRegionsPaths)
         {
             if (DateTime.Now - print > TimeSpan.FromSeconds(2))
@@ -198,7 +198,8 @@ public class Converter(float regionSize, string? exportFolderPath = null, ILogge
                     {
                         waysStreamWriter.WriteLine(line);
                         wayIds.Add(w.ID);
-                        nodeIds.AddRange(w.NodeIds);
+                        foreach (ulong nodeId in w.NodeIds)
+                            nodeIds.Add(nodeId);
                         hasWritten = true;
                     }else
                         logger?.LogTrace($"Way {w.ID} is not a highway. BYE!");