diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MarshallingSessionHandler.php b/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MarshallingSessionHandler.php
index e1cad6a9454e5..c321c8c932377 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MarshallingSessionHandler.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MarshallingSessionHandler.php
@@ -30,6 +30,7 @@ public function __construct(AbstractSessionHandler $handler, MarshallerInterface
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function open($savePath, $name)
     {
         return $this->handler->open($savePath, $name);
@@ -38,6 +39,7 @@ public function open($savePath, $name)
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function close()
     {
         return $this->handler->close();
@@ -46,14 +48,16 @@ public function close()
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function destroy($sessionId)
     {
         return $this->handler->destroy($sessionId);
     }
 
     /**
-     * @return bool
+     * @return int|false
      */
+    #[\ReturnTypeWillChange]
     public function gc($maxlifetime)
     {
         return $this->handler->gc($maxlifetime);
@@ -62,6 +66,7 @@ public function gc($maxlifetime)
     /**
      * @return string
      */
+    #[\ReturnTypeWillChange]
     public function read($sessionId)
     {
         return $this->marshaller->unmarshall($this->handler->read($sessionId));
@@ -70,6 +75,7 @@ public function read($sessionId)
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function write($sessionId, $data)
     {
         $failed = [];
@@ -85,6 +91,7 @@ public function write($sessionId, $data)
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function validateId($sessionId)
     {
         return $this->handler->validateId($sessionId);
@@ -93,6 +100,7 @@ public function validateId($sessionId)
     /**
      * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function updateTimestamp($sessionId, $data)
     {
         return $this->handler->updateTimestamp($sessionId, $data);
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MarshallingSessionHandlerTest.php b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MarshallingSessionHandlerTest.php
index db8c7432707c0..7216cdd1ece74 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MarshallingSessionHandlerTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MarshallingSessionHandlerTest.php
@@ -72,7 +72,7 @@ public function testGc()
         $marshallingSessionHandler = new MarshallingSessionHandler($this->handler, $this->marshaller);
 
         $this->handler->expects($this->once())->method('gc')
-            ->with(4711)->willReturn(true);
+            ->with(4711)->willReturn(1);
 
         $marshallingSessionHandler->gc(4711);
     }
diff --git a/src/Symfony/Component/VarDumper/Tests/Caster/CasterTest.php b/src/Symfony/Component/VarDumper/Tests/Caster/CasterTest.php
index f0a1fbbe8b045..c39e82cf6adb0 100644
--- a/src/Symfony/Component/VarDumper/Tests/Caster/CasterTest.php
+++ b/src/Symfony/Component/VarDumper/Tests/Caster/CasterTest.php
@@ -164,7 +164,7 @@ public function testAnonymousClass()
             , $c
         );
 
-        $c = eval('return new class implements \Countable { private $foo = "foo"; public function count() { return 0; } };');
+        $c = eval('return new class implements \Countable { private $foo = "foo"; public function count(): int { return 0; } };');
 
         $this->assertDumpMatchesFormat(
             <<<'EOTXT'