diff --git a/src/Message/PlainMessage.php b/src/Message/PlainMessage.php
index 00590424..a2acf1bb 100644
--- a/src/Message/PlainMessage.php
+++ b/src/Message/PlainMessage.php
@@ -9,18 +9,15 @@
 /**
  * Simple message that gets you started.
  * It has a name and an array of arguments.
- * It does not enforce any types or properties so be careful on relying them
+ * It does not enforce any types or properties so be careful relying on them
  * being there.
  */
 final class PlainMessage implements Message, \ArrayAccess
 {
-    private $name;
-    private $arguments;
+    private string $name;
+    private array $arguments;
 
-    /**
-     * @param string $name
-     */
-    public function __construct($name, array $arguments = [])
+    public function __construct(string $name, array $arguments = [])
     {
         $this->name = $name;
         $this->arguments = $arguments;
@@ -29,59 +26,48 @@ public function __construct($name, array $arguments = [])
     /**
      * {@inheritdoc}
      */
-    public function getName()
+    public function getName() : string
     {
         return $this->name;
     }
 
-    /**
-     * @return array
-     */
-    public function all()
+    public function all() : array
     {
         return $this->arguments;
     }
 
     /**
      * Returns the argument if found or null.
-     *
-     * @param string $name
-     *
-     * @return mixed
      */
-    public function get($name)
+    public function get(string $name) : mixed
     {
         return $this->has($name) ? $this->arguments[$name] : null;
     }
 
     /**
      * Checks whether the arguments contain the given key.
-     *
-     * @param string $name
-     *
-     * @return bool
      */
-    public function has($name)
+    public function has(string $name) : bool
     {
         return \array_key_exists($name, $this->arguments);
     }
 
-    public function offsetGet($offset)
+    public function offsetGet(mixed $offset) : mixed
     {
         return $this->get($offset);
     }
 
-    public function offsetExists($offset)
+    public function offsetExists(mixed $offset) : bool
     {
         return $this->has($offset);
     }
 
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         throw new \LogicException('Message is immutable');
     }
 
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         throw new \LogicException('Message is immutable');
     }
diff --git a/src/Queue/PersistentQueue.php b/src/Queue/PersistentQueue.php
index 6057a05e..d6d9cc5d 100644
--- a/src/Queue/PersistentQueue.php
+++ b/src/Queue/PersistentQueue.php
@@ -7,23 +7,21 @@
 use Bernard\Driver;
 use Bernard\Envelope;
 use Bernard\Serializer;
+use SplObjectStorage;
 
 class PersistentQueue extends AbstractQueue
 {
-    protected $driver;
-    protected $serializer;
-    protected $receipts;
-
-    /**
-     * @param string $name
-     */
-    public function __construct($name, Driver $driver, Serializer $serializer)
+    protected Driver $driver;
+    protected Serializer $serializer;
+    protected SplObjectStorage $receipts;
+    
+    public function __construct(string $name, Driver $driver, Serializer $serializer)
     {
         parent::__construct($name);
 
         $this->driver = $driver;
         $this->serializer = $serializer;
-        $this->receipts = new \SplObjectStorage();
+        $this->receipts = new SplObjectStorage();
 
         $this->register();
     }
@@ -41,7 +39,7 @@ public function register(): void
     /**
      * {@inheritdoc}
      */
-    public function count()
+    public function count() : int
     {
         $this->errorIfClosed();