diff --git a/src/Shortid.php b/src/Shortid.php
index 90e2cd9..33c7c6d 100644
--- a/src/Shortid.php
+++ b/src/Shortid.php
@@ -4,7 +4,7 @@
 
 final class Shortid implements \JsonSerializable, \Serializable, \Stringable
 {
-    private static ?Factory $factory;
+    private static ?Factory $factory = null;
 
     /**
      * @throws InvalidShortidException