diff --git a/app/src/main/java/gui/menu/MultiPlayerView.java b/app/src/main/java/gui/menu/MultiPlayerView.java
index 9a0ee2e..e58f24d 100644
--- a/app/src/main/java/gui/menu/MultiPlayerView.java
+++ b/app/src/main/java/gui/menu/MultiPlayerView.java
@@ -1,9 +1,12 @@
 package gui.menu;
 
+import java.util.Arrays;
+
 import game.Player;
 import imgui.ImGui;
 import network.client.Client;
 import network.server.Server;
+import sudoku.constraint.Constraint;
 import sudoku.structure.MultiDoku;
 import sudoku.structure.SudokuFactory;
 
@@ -37,7 +40,7 @@ public class MultiPlayerView extends BaseView {
 		} else {
 			if (ImGui.button("Démarrer")) {
 				// temp
-				MultiDoku doku = SudokuFactory.createBasicXShapedMultidoku(3, SudokuFactory.DEFAULT_CONSTRAINTS);
+				MultiDoku doku = SudokuFactory.createBasicXShapedMultidoku(3, Arrays.asList(Constraint.Diagonal));
 				this.server.startGame(doku);
 			}
 		}
diff --git a/app/src/main/java/sudoku/io/SudokuSerializer.java b/app/src/main/java/sudoku/io/SudokuSerializer.java
index 366342d..a71e4f3 100644
--- a/app/src/main/java/sudoku/io/SudokuSerializer.java
+++ b/app/src/main/java/sudoku/io/SudokuSerializer.java
@@ -10,6 +10,7 @@ import java.util.List;
 import org.json.JSONArray;
 import org.json.JSONObject;
 
+import sudoku.constraint.Constraint;
 import sudoku.structure.Block;
 import sudoku.structure.Cell;
 import sudoku.structure.MultiDoku;
@@ -73,6 +74,7 @@ public class SudokuSerializer {
 			JSONObject jsonSudoku = new JSONObject();
 			JSONArray cellsJsonArray = new JSONArray();
 			JSONArray blocksJsonArray = new JSONArray();
+			JSONArray constraintsJsonArray = new JSONArray();
 
 			Sudoku sudoku = multidoku.getSubGrid(i);
 
@@ -90,6 +92,13 @@ public class SudokuSerializer {
 				blocksJsonArray.put(blockID);
 			}
 
+			// serialize constraints
+
+			for (Constraint cons : sudoku.getConstraints()) {
+				constraintsJsonArray.put(cons.ordinal());
+			}
+
+			jsonSudoku.put("constraints", constraintsJsonArray);
 			jsonSudoku.put("cells", cellsJsonArray);
 			jsonSudoku.put("blocks", blocksJsonArray);
 			jsonSudoku.put("blockWidth", sudoku.getBlockWidth());
@@ -211,9 +220,11 @@ public class SudokuSerializer {
 			JSONObject sudokuJsonObject = multidokuJsonObject.getJSONObject(i);
 			JSONArray sudokuCellsJsonArray = sudokuJsonObject.getJSONArray("cells");
 			JSONArray sudokuBlocksJsonArray = sudokuJsonObject.getJSONArray("blocks");
+			JSONArray sudokuConstraintsJsonArray = sudokuJsonObject.getJSONArray("constraints");
 
 			List<Cell> sudokuCells = new ArrayList<>();
 			List<Block> sudokuBlocks = new ArrayList<>();
+			List<Constraint> sudokuConstraints = new ArrayList<>();
 
 			for (int j = 0; j < sudokuCellsJsonArray.length(); j++) {
 				int cellID = sudokuCellsJsonArray.getInt(j);
@@ -225,7 +236,12 @@ public class SudokuSerializer {
 				sudokuBlocks.add(blocks.get(blockID));
 			}
 
-			Sudoku s = new Sudoku(sudokuCells, sudokuBlocks, SudokuFactory.DEFAULT_CONSTRAINTS);
+			for (int j = 0; j < sudokuConstraintsJsonArray.length(); j++) {
+				int constraintID = sudokuConstraintsJsonArray.getInt(j);
+				sudokuConstraints.add(Constraint.values()[constraintID]);
+			}
+
+			Sudoku s = new Sudoku(sudokuCells, sudokuBlocks, sudokuConstraints);
 			s.setBlockWidth(sudokuJsonObject.getInt("blockWidth"));
 			sudokus.add(s);
 		}