diff --git a/phpunit.xml b/phpunit.xml
index 28a1efd..a44d963 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/8.1/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/8.5/phpunit.xsd"
          bootstrap="vendor/autoload.php"
          executionOrder="depends,defects"
          cacheResult="false"
diff --git a/tests/Stub/StubTerminableCommand.php b/tests/Stub/StubTerminableCommand.php
index 0378d9b..99ad98a 100644
--- a/tests/Stub/StubTerminableCommand.php
+++ b/tests/Stub/StubTerminableCommand.php
@@ -19,8 +19,8 @@ public function __construct()
 
     public function configure(): void
     {
-        $this->addOption('stub', null, InputOption::VALUE_REQUIRED, 'Stubbed execution duration time', 0);
-        $this->addOption('sleep', null, InputOption::VALUE_REQUIRED, 'Sleep duration time', 0);
+        $this->addOption('stub', null, InputOption::VALUE_REQUIRED, 'Stubbed execution duration time', '0');
+        $this->addOption('sleep', null, InputOption::VALUE_REQUIRED, 'Sleep duration time', '0');
     }
 
     protected function commandBody(InputInterface $input, OutputInterface $output): int