diff --git a/src/Doctrine/EntityRelation.php b/src/Doctrine/EntityRelation.php
index adb3546d83..91db3effce 100644
--- a/src/Doctrine/EntityRelation.php
+++ b/src/Doctrine/EntityRelation.php
@@ -27,7 +27,7 @@ final class EntityRelation
     private bool $isSelfReferencing = false;
     private bool $orphanRemoval = false;
     private bool $mapInverseRelation = true;
-    private ?string $joinTableName;
+    private ?string $joinTableName = null;
 
     public function __construct(
         private string $type,