diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 720428ac..e212566e 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -15,7 +15,7 @@ class Configuration implements ConfigurationInterface
     /**
      * {@inheritdoc}
      */
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('apy_data_grid');
         $rootNode = $treeBuilder->getRootNode();