diff --git a/Chess-Challenge/src/Framework/Chess/Board/Board.cs b/Chess-Challenge/src/Framework/Chess/Board/Board.cs
index 3d1daef..bb6d906 100644
--- a/Chess-Challenge/src/Framework/Chess/Board/Board.cs
+++ b/Chess-Challenge/src/Framework/Chess/Board/Board.cs
@@ -68,7 +68,7 @@ namespace ChessChallenge.Chess
 
 
 
-        public Board(Board source = null)
+        public Board(Board? source = null)
         {
             if (source != null)
             {