diff --git a/src/Command/WebPushGenerateKeysCommand.php b/src/Command/WebPushGenerateKeysCommand.php
index 7aea684..96b0a15 100644
--- a/src/Command/WebPushGenerateKeysCommand.php
+++ b/src/Command/WebPushGenerateKeysCommand.php
@@ -18,7 +18,7 @@ final class WebPushGenerateKeysCommand extends Command
     /**
      * {@inheritdoc}
      */
-    protected function configure()
+    protected function configure(): void
     {
         $this
             ->setName('webpush:generate:keys')