diff --git a/Grille.php b/Grille.php
index 8e92378..1eb166c 100644
--- a/Grille.php
+++ b/Grille.php
@@ -66,8 +66,8 @@ class Grille implements ArrayAccess
 
         if (!isset($this->positions)) {
             $this->positions = [];
-            for ($y = 0; $y < $hauteur; $y++) {
-                for ($x = 0; $x < $largeur; $x++)
+            for ($y = 0; $y < $this->hauteur; $y++) {
+                for ($x = 0; $x < $this->largeur; $x++)
                     $this->positions[] = [$x, $y];
             }
             $this->nb_positions = count($this->positions);
diff --git a/index.php b/index.php
index 7aaf9f4..ef97dac 100644
--- a/index.php
+++ b/index.php
@@ -134,7 +134,7 @@ function formatter_definition($definition) {
                                     <?php else: ?>
                                         <td class="case blanche">
                                             <input id="<?= chr($x + 65) . ($y + 1) ?>" type="text" maxlength="1" size="1" pattern="[A-Z]" placeholder="<?= $grille[$y][$x] ?>"
-                                                title="<?= strip_tags("→ " . implode("\n→ ", array_map("formatter_definition", $grille->definitions["horizontales"][$y])) . "\n↓ " . implode("\n↓ ", array_map("formatter_definition", $grille->definitions["verticales"][$x]))) ?>" />
+                                                title="<?= strip_tags("→ " . implode("\n→ ", array_map("formatter_definition", $grille->definitions["horizontales"][$y] ?? [])) . "\n↓ " . implode("\n↓ ", array_map("formatter_definition", $grille->definitions["verticales"][$x] ?? []))) ?>" />
                                         </td>
                                     <?php endif; ?>
                                 <?php endfor; ?>