diff --git a/composer.json b/composer.json
index 6899768..4fe8e19 100644
--- a/composer.json
+++ b/composer.json
@@ -7,13 +7,13 @@
     "performance"
   ],
   "require": {
-    "composer/xdebug-handler": "^1.3 || ^2.0",
-    "php": "~5.3 || ~7.0 || ~8.0"
+    "composer/xdebug-handler": "^1.3 || ^2.0 || ^3.0",
+    "php": "~7.1 || ~8.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0 || ^8.0 || ^9.0",
+    "phpunit/phpunit": "^7.0 || ^8.0 || ^9.0",
     "ext-xdebug": "*",
-    "php": "~5.6 || ~7.0 || ~8.0",
+    "php": "~7.1 || ~8.0",
     "squizlabs/php_codesniffer": "^3.3",
     "php-parallel-lint/php-parallel-lint": "^1.3"
   },
diff --git a/src/Restarter.php b/src/Restarter.php
index 19af8bc..c1640d9 100644
--- a/src/Restarter.php
+++ b/src/Restarter.php
@@ -6,7 +6,7 @@
 
 class Restarter extends XdebugHandler
 {
-    protected function restart($command)
+    protected function restart($command): void
     {
         assert(null !== $this->tmpIni);
         $contents = file_get_contents($this->tmpIni);