diff --git a/src/Mapping/PropertyMapping.php b/src/Mapping/PropertyMapping.php
index c7f465d0..17babfe3 100644
--- a/src/Mapping/PropertyMapping.php
+++ b/src/Mapping/PropertyMapping.php
@@ -290,9 +290,9 @@ public function getUploadName(object $obj): string
      *
      * @param object $obj
      *
-     * @return string|null The upload directory
+     * @return string The upload directory
      */
-    public function getUploadDir($obj): ?string
+    public function getUploadDir($obj): string
     {
         if (!$this->hasDirectoryNamer()) {
             return '';