diff --git a/src/PhpSigep/Cache/Storage/Adapter/AdapterOptions.php b/src/PhpSigep/Cache/Storage/Adapter/AdapterOptions.php
index b02d1a308f..55934ca91b 100644
--- a/src/PhpSigep/Cache/Storage/Adapter/AdapterOptions.php
+++ b/src/PhpSigep/Cache/Storage/Adapter/AdapterOptions.php
@@ -49,7 +49,7 @@ class AdapterOptions extends DefaultStdClass
      * @param  StorageInterface|null $adapter
      * @return AdapterOptions
      */
-    public function setAdapter(StorageInterface $adapter = null)
+    public function setAdapter(?StorageInterface $adapter = null)
     {
         $this->adapter = $adapter;