diff --git a/lib/Ebook.php b/lib/Ebook.php
index bd82097d..1670c597 100644
--- a/lib/Ebook.php
+++ b/lib/Ebook.php
@@ -935,7 +935,7 @@ class Ebook{
 	// ORM METHODS
 	// ***********
 
-	public static function GetByIdentifier(?string $identifier): ?Ebook{
+	public static function GetByIdentifier(?string $identifier): Ebook{
 		if($identifier === null){
 			throw new Exceptions\EbookNotFoundException('Invalid identifier: ' . $identifier);
 		}