diff --git a/src/main/java/model/GridIterator.java b/src/main/java/model/GridIterator.java
index 549cc9158568a185b6c7fa33c78fedb0ccc29850..92b7dd242ba806d0e78abeeef975327805b8e2ce 100644
--- a/src/main/java/model/GridIterator.java
+++ b/src/main/java/model/GridIterator.java
@@ -8,7 +8,7 @@ import java.util.Iterator;
 public class GridIterator implements Iterator<Cell> {
     private int rowIndex;
     private int columnIndex;
-    private Grid grid;
+    private final Grid grid;
 
     GridIterator(Grid grid) {
         this.rowIndex = 0;