diff --git a/src/Controllers/Modal.php b/src/Controllers/Modal.php
index e1d9989..31f1446 100644
--- a/src/Controllers/Modal.php
+++ b/src/Controllers/Modal.php
@@ -14,7 +14,7 @@ public function __construct(?string $customKey = null, bool $open = false)
         $this->open = $open;
 
         // replace all characters except letters, numbers , _ and - to _
-        $this->customKey = preg_replace('/[^a-zA-Z0-9_-]/', '_', $customKey);
+        $this->customKey = $customKey ? preg_replace('/[^a-zA-Z0-9_-]/', '_', $customKey) : null;
     }
 
     public static function make(?string $customKey = null): Modal