diff --git a/src/Ouzo/Core/Tests/MockDownloadHandler.php b/src/Ouzo/Core/Tests/MockDownloadHandler.php
index 5c661aea3..2871b28d5 100644
--- a/src/Ouzo/Core/Tests/MockDownloadHandler.php
+++ b/src/Ouzo/Core/Tests/MockDownloadHandler.php
@@ -10,9 +10,9 @@
 
 class MockDownloadHandler
 {
-    private $fileData;
+    private $fileData = [];
 
-    public function downloadFile($fileData)
+    public function downloadFile(array $fileData)
     {
         $this->fileData = $fileData;
         return $this;