diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index d5b9d46..6a5a402 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -7,7 +7,7 @@
 
 class Configuration implements ConfigurationInterface
 {
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('intaro_file_uploader');
         if (\method_exists($treeBuilder, 'getRootNode')) {