diff --git a/src/main/java/darks/grid/manager/GridStorageManager.java b/src/main/java/darks/grid/manager/GridStorageManager.java
index e0cacc8..1ff0696 100644
--- a/src/main/java/darks/grid/manager/GridStorageManager.java
+++ b/src/main/java/darks/grid/manager/GridStorageManager.java
@@ -20,7 +20,10 @@
 import java.io.File;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 import darks.grid.config.GridConfiguration;
 import darks.grid.utils.FileUtils;
@@ -63,12 +66,12 @@ public synchronized void cacheHistoryNodes(InetSocketAddress address)
 		FileUtils.appendLine(historyNodesFile, addr);
 	}
 	
-	public synchronized List<InetSocketAddress> getCacheHistoryNodes()
+	public synchronized Collection<InetSocketAddress> getCacheHistoryNodes()
 	{
 		if (historyNodesFile.exists())
 		{
 			List<String> addresses = FileUtils.readLineToList(historyNodesFile);
-			List<InetSocketAddress> result = new ArrayList<>(addresses.size());
+			Set<InetSocketAddress> result = new HashSet<>(addresses.size());
 			for (String addr : addresses)
 			{
 				String[] datas = addr.split(":");
diff --git a/src/main/java/darks/grid/network/discovery/TCPPING.java b/src/main/java/darks/grid/network/discovery/TCPPING.java
index b555152..87236a1 100644
--- a/src/main/java/darks/grid/network/discovery/TCPPING.java
+++ b/src/main/java/darks/grid/network/discovery/TCPPING.java
@@ -18,9 +18,7 @@
 
 import java.net.InetSocketAddress;
 import java.util.Collection;
-import java.util.HashSet;
 import java.util.LinkedHashSet;
-import java.util.List;
 import java.util.Set;
 
 import org.slf4j.Logger;
@@ -60,7 +58,7 @@ public void findNodes()
 				tryAddrs.add(address);
 			}
 		}
-		List<InetSocketAddress> cacheAddrs = GridRuntime.storage().getCacheHistoryNodes();
+		Collection<InetSocketAddress> cacheAddrs = GridRuntime.storage().getCacheHistoryNodes();
 		if (cacheAddrs != null)
 		{
 			for (InetSocketAddress address : cacheAddrs)