diff --git a/src/Markup.php b/src/Markup.php
index 19ba9baac..0cc45bef1 100644
--- a/src/Markup.php
+++ b/src/Markup.php
@@ -41,6 +41,9 @@ class Markup implements \Countable, \JsonSerializable
         return mb_strlen($this->content, $this->charset);
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
diff --git a/src/Util/TemplateDirIterator.php b/src/Util/TemplateDirIterator.php
index 1ab0dac59..b0356d4c2 100644
--- a/src/Util/TemplateDirIterator.php
+++ b/src/Util/TemplateDirIterator.php
@@ -16,11 +16,19 @@ namespace Twig\Util;
  */
 class TemplateDirIterator extends \IteratorIterator
 {
+    /**
+     * @return mixed
+     */
+    #[\ReturnTypeWillChange]
     public function current()
     {
         return file_get_contents(parent::current());
     }
 
+    /**
+     * @return mixed
+     */
+    #[\ReturnTypeWillChange]
     public function key()
     {
         return (string) parent::key();
diff --git a/tests/Extension/CoreTest.php b/tests/Extension/CoreTest.php
index 40255fefa..5f82ccad5 100644
--- a/tests/Extension/CoreTest.php
+++ b/tests/Extension/CoreTest.php
@@ -305,6 +305,9 @@ final class CoreTestIterator implements \Iterator
         $this->position = 0;
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function current()
     {
@@ -315,6 +318,9 @@ final class CoreTestIterator implements \Iterator
         throw new \LogicException('Code should only use the keys, not the values provided by iterator.');
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function key()
     {
diff --git a/tests/IntegrationTest.php b/tests/IntegrationTest.php
index 4b82c9bb6..79674d1fc 100644
--- a/tests/IntegrationTest.php
+++ b/tests/IntegrationTest.php
@@ -104,12 +104,18 @@ class TwigTestFoo implements \Iterator
         $this->position = 0;
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function current()
     {
         return $this->array[$this->position];
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function key()
     {
@@ -363,6 +369,9 @@ class SimpleIteratorForTesting implements \Iterator
     private $data = [1, 2, 3, 4, 5, 6, 7];
     private $key = 0;
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function current()
     {
@@ -374,6 +383,9 @@ class SimpleIteratorForTesting implements \Iterator
         ++$this->key;
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function key()
     {
diff --git a/tests/TemplateTest.php b/tests/TemplateTest.php
index f586027a1..f256ebfd5 100644
--- a/tests/TemplateTest.php
+++ b/tests/TemplateTest.php
@@ -476,6 +476,9 @@ class TemplateArrayAccessObject implements \ArrayAccess
         return \array_key_exists($name, $this->attributes);
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function offsetGet($name)
     {
@@ -509,7 +512,7 @@ class TemplateMagicPropertyObject
 
     protected $protected = 'protected';
 
-    public function __isset($name)
+    public function __isset($name): bool
     {
         return \array_key_exists($name, $this->attributes);
     }
@@ -522,7 +525,7 @@ class TemplateMagicPropertyObject
 
 class TemplateMagicPropertyObjectWithException
 {
-    public function __isset($key)
+    public function __isset($key): bool
     {
         throw new \Exception('Hey! Don\'t try to isset me!');
     }
@@ -566,6 +569,9 @@ class TemplatePropertyObjectAndArrayAccess extends TemplatePropertyObject implem
         return \array_key_exists($offset, $this->data);
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
@@ -715,6 +721,9 @@ class TemplateArrayAccess implements \ArrayAccess
         return \array_key_exists($offset, $this->children);
     }
 
+    /**
+     * @return mixed
+     */
     #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {