diff --git a/app/src/main/java/sudoku/structure/MultiDoku.java b/app/src/main/java/sudoku/structure/MultiDoku.java
index ecee5fd..a1ea69a 100644
--- a/app/src/main/java/sudoku/structure/MultiDoku.java
+++ b/app/src/main/java/sudoku/structure/MultiDoku.java
@@ -198,5 +198,11 @@ public class MultiDoku {
 		}
 		return result;
 	}
+
+	public void setFilledCellsImmutable() {
+		for (Cell filledCell : getFilledCells()) {
+			filledCell.setImmutable();
+		}
+	}
 }
 
diff --git a/app/src/main/java/sudoku/structure/SudokuFactory.java b/app/src/main/java/sudoku/structure/SudokuFactory.java
index f0cdb0f..7b843b3 100644
--- a/app/src/main/java/sudoku/structure/SudokuFactory.java
+++ b/app/src/main/java/sudoku/structure/SudokuFactory.java
@@ -217,7 +217,7 @@ public class SudokuFactory {
 	public static MultiDoku createBasicXShapedMultidoku(int size) {
 		assert (size > 1);
 
-		/**
+		/*
 		 * 2 3
 		 *  1
 		 * 4 5
@@ -245,6 +245,7 @@ public class SudokuFactory {
 		if (!successfull) {
 			throw new Exception("Canno't create this doku with this difficulty");
 		}
+		doku.setFilledCellsImmutable();
 		return doku;
 	}
 
@@ -260,6 +261,7 @@ public class SudokuFactory {
 		if (!successful) {
 			throw new Exception("Cannot create this Doku with this difficulty");
 		}
+		doku.setFilledCellsImmutable();
 		return doku;
 	}
 }