diff --git a/src/Message/MessagePart.php b/src/Message/MessagePart.php
index f0434267..ad05269f 100644
--- a/src/Message/MessagePart.php
+++ b/src/Message/MessagePart.php
@@ -57,18 +57,27 @@ public function __construct(PartStreamContainer $streamContainer, IMimePart $par
         $this->observers = new SplObjectStorage();
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function attach(SplObserver $observer)
     {
         $this->observers->attach($observer);
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function detach(SplObserver $observer)
     {
         $this->observers->detach($observer);
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function notify()
     {
diff --git a/src/Message/PartChildrenContainer.php b/src/Message/PartChildrenContainer.php
index 8df7e458..94b7bf90 100644
--- a/src/Message/PartChildrenContainer.php
+++ b/src/Message/PartChildrenContainer.php
@@ -131,18 +131,27 @@ public function remove(IMessagePart $part)
         return null;
     }
 
+    /**
+     * @return bool
+     */
     #[\ReturnTypeWillChange]
     public function offsetExists($offset)
     {
         return isset($this->children[$offset]);
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
         return $this->offsetExists($offset) ? $this->children[$offset] : null;
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function offsetSet($offset, $value)
     {
@@ -158,6 +167,9 @@ public function offsetSet($offset, $value)
         }
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function offsetUnset($offset)
     {
diff --git a/src/Parser/Part/ParserPartStreamContainer.php b/src/Parser/Part/ParserPartStreamContainer.php
index 46a4e7ad..d8d92d11 100644
--- a/src/Parser/Part/ParserPartStreamContainer.php
+++ b/src/Parser/Part/ParserPartStreamContainer.php
@@ -143,6 +143,9 @@ public function getStream()
         return parent::getStream();
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function update(SplSubject $subject)
     {
diff --git a/src/Stream/MessagePartStream.php b/src/Stream/MessagePartStream.php
index f130762c..c010fc35 100644
--- a/src/Stream/MessagePartStream.php
+++ b/src/Stream/MessagePartStream.php
@@ -59,6 +59,9 @@ public function __destruct()
         }
     }
 
+    /**
+     * @return void
+     */
     #[\ReturnTypeWillChange]
     public function update(SplSubject $subject)
     {