diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 03ee73b..06de471 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -10,7 +10,7 @@
 
 class Configuration implements ConfigurationInterface
 {
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('frosh_sentry');
         $rootNode = $treeBuilder->getRootNode();