diff --git a/SearchBox/InvertedIndex.cs b/SearchBox/InvertedIndex.cs
index f31e413..baa7c1f 100644
--- a/SearchBox/InvertedIndex.cs
+++ b/SearchBox/InvertedIndex.cs
@@ -6,7 +6,7 @@ namespace SearchBox
 {
 	public class InvertedIndex
 	{
-		private ConcurrentDictionary<string, ConcurrentDictionary<int, List<int>>> invertedIndex = new Dictionary<string, Dictionary<int, List<int>>>();
+		private ConcurrentDictionary<string, ConcurrentDictionary<int, List<int>>> invertedIndex = new ConcurrentDictionary<string, ConcurrentDictionary<int, List<int>>>();
 
 		public InvertedIndex()
 		{