diff --git a/.travis.yml b/.travis.yml
index e1ef244..e71d942 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,9 @@ php:
   - 7.1
   - 7.2
   - 7.3
+  - 8.0
+  - 8.1
+  - 8.2
 
 script:
   - ./vendor/bin/phpunit
diff --git a/composer.json b/composer.json
index eba75d0..f17695d 100644
--- a/composer.json
+++ b/composer.json
@@ -3,11 +3,11 @@
     "description": "Remove aliases from email and get primary email account",
     "type": "library",
     "require": {
-        "php": "^7.0.0",
+        "php": "^8.0.0",
         "ext-mbstring": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "6.5.14",
+        "phpunit/phpunit": "^9.0.0",
         "satooshi/php-coveralls": "^1.0.1",
         "codacy/coverage": "^1.0.3"
     },
diff --git a/src/ServiceCollector.php b/src/ServiceCollector.php
index 8258942..de11c3f 100644
--- a/src/ServiceCollector.php
+++ b/src/ServiceCollector.php
@@ -10,18 +10,18 @@ class ServiceCollector implements ServiceCollectorInterface
 {
     private $services = [];
 
-    public function addService(ServiceInterface $service)
+    public function addService(ServiceInterface $service): void
     {
         $this->services[] = $service;
     }
 
     /**
-     * @inheritdoc
+     * {@inheritdoc}
      */
-    public function getIterator()
+    public function getIterator(): \Traversable
     {
         foreach ($this->services as $service) {
             yield $service;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/ServiceCollectorInterface.php b/src/ServiceCollectorInterface.php
index 9d98605..0b3f06e 100644
--- a/src/ServiceCollectorInterface.php
+++ b/src/ServiceCollectorInterface.php
@@ -9,5 +9,5 @@ interface ServiceCollectorInterface extends \IteratorAggregate
     /**
      * @return ServiceInterface[]
      */
-    public function getIterator();
-}
\ No newline at end of file
+    public function getIterator(): \Traversable;
+}