diff --git a/src/Symfony/Component/VarExporter/Internal/Exporter.php b/src/Symfony/Component/VarExporter/Internal/Exporter.php
index 87b3156d41ef..c0b7fa17f44c 100644
--- a/src/Symfony/Component/VarExporter/Internal/Exporter.php
+++ b/src/Symfony/Component/VarExporter/Internal/Exporter.php
@@ -155,7 +155,7 @@ public static function prepare($values, $objectsPool, &$refsPool, &$objectsCount
                     }
                     $sleep[$n] = false;
                 }
-                if (!\array_key_exists($name, $proto) || $proto[$name] !== $v) {
+                if (!\array_key_exists($name, $proto) || $proto[$name] !== $v || "\x00Error\x00trace" === $name || "\x00Exception\x00trace" === $name) {
                     $properties[$c][$n] = $v;
                 }
             }
@@ -291,7 +291,7 @@ private static function exportRegistry(Registry $value, string $indent, string $
                 continue;
             }
             if (!Registry::$instantiableWithoutConstructor[$class]) {
-                if (is_subclass_of($class, 'Serializable')) {
+                if (is_subclass_of($class, 'Serializable') && !method_exists($class, '__unserialize')) {
                     $serializables[$k] = 'C:'.\strlen($class).':"'.$class.'":0:{}';
                 } else {
                     $serializables[$k] = 'O:'.\strlen($class).':"'.$class.'":0:{}';
diff --git a/src/Symfony/Component/VarExporter/Internal/Registry.php b/src/Symfony/Component/VarExporter/Internal/Registry.php
index dd2792133e42..19d91c930411 100644
--- a/src/Symfony/Component/VarExporter/Internal/Registry.php
+++ b/src/Symfony/Component/VarExporter/Internal/Registry.php
@@ -75,7 +75,7 @@ public static function getClassReflector($class, $instantiableWithoutConstructor
         } elseif (!$isClass || $reflector->isAbstract()) {
             throw new NotInstantiableTypeException($class);
         } elseif ($reflector->name !== $class) {
-            $reflector = self::$reflectors[$name = $reflector->name] ?? self::getClassReflector($name, $instantiableWithoutConstructor, $cloneable);
+            $reflector = self::$reflectors[$name = $reflector->name] ?? self::getClassReflector($name, false, $cloneable);
             self::$cloneable[$class] = self::$cloneable[$name];
             self::$instantiableWithoutConstructor[$class] = self::$instantiableWithoutConstructor[$name];
             self::$prototypes[$class] = self::$prototypes[$name];
@@ -86,7 +86,7 @@ public static function getClassReflector($class, $instantiableWithoutConstructor
                 $proto = $reflector->newInstanceWithoutConstructor();
                 $instantiableWithoutConstructor = true;
             } catch (\ReflectionException $e) {
-                $proto = $reflector->implementsInterface('Serializable') && (\PHP_VERSION_ID < 70400 || !method_exists($class, '__unserialize')) ? 'C:' : 'O:';
+                $proto = $reflector->implementsInterface('Serializable') && !method_exists($class, '__unserialize') ? 'C:' : 'O:';
                 if ('C:' === $proto && !$reflector->getMethod('unserialize')->isInternal()) {
                     $proto = null;
                 } elseif (false === $proto = @unserialize($proto.\strlen($class).':"'.$class.'":0:{}')) {
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator-legacy.php
new file mode 100644
index 000000000000..c59573315d18
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator-legacy.php
@@ -0,0 +1,22 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = [
+        clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['ArrayIterator'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('ArrayIterator')),
+    ],
+    null,
+    [
+        'ArrayIterator' => [
+            "\0" => [
+                [
+                    [
+                        123,
+                    ],
+                    1,
+                ],
+            ],
+        ],
+    ],
+    $o[0],
+    []
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator.php
index c59573315d18..ed4df00c99e5 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-iterator.php
@@ -5,18 +5,15 @@
         clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['ArrayIterator'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('ArrayIterator')),
     ],
     null,
+    [],
+    $o[0],
     [
-        'ArrayIterator' => [
-            "\0" => [
-                [
-                    [
-                        123,
-                    ],
-                    1,
-                ],
+        [
+            1,
+            [
+                123,
             ],
+            [],
         ],
-    ],
-    $o[0],
-    []
+    ]
 );
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom-legacy.php
new file mode 100644
index 000000000000..35303f822214
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom-legacy.php
@@ -0,0 +1,22 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = [
+        clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['Symfony\\Component\\VarExporter\\Tests\\MyArrayObject'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('Symfony\\Component\\VarExporter\\Tests\\MyArrayObject')),
+    ],
+    null,
+    [
+        'ArrayObject' => [
+            "\0" => [
+                [
+                    [
+                        234,
+                    ],
+                    1,
+                ],
+            ],
+        ],
+    ],
+    $o[0],
+    []
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom.php
index 35303f822214..530f0d1026ec 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-custom.php
@@ -5,18 +5,17 @@
         clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['Symfony\\Component\\VarExporter\\Tests\\MyArrayObject'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('Symfony\\Component\\VarExporter\\Tests\\MyArrayObject')),
     ],
     null,
+    [],
+    $o[0],
     [
-        'ArrayObject' => [
-            "\0" => [
-                [
-                    [
-                        234,
-                    ],
-                    1,
-                ],
+        [
+            1,
+            [
+                234,
+            ],
+            [
+                "\0".'Symfony\\Component\\VarExporter\\Tests\\MyArrayObject'."\0".'unused' => 123,
             ],
         ],
-    ],
-    $o[0],
-    []
+    ]
 );
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-legacy.php
new file mode 100644
index 000000000000..a461c6ed97f7
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object-legacy.php
@@ -0,0 +1,29 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = [
+        clone (($p = &\Symfony\Component\VarExporter\Internal\Registry::$prototypes)['ArrayObject'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('ArrayObject')),
+        clone $p['ArrayObject'],
+    ],
+    null,
+    [
+        'ArrayObject' => [
+            "\0" => [
+                [
+                    [
+                        1,
+                        $o[0],
+                    ],
+                    0,
+                ],
+            ],
+        ],
+        'stdClass' => [
+            'foo' => [
+                $o[1],
+            ],
+        ],
+    ],
+    $o[0],
+    []
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object.php
index a461c6ed97f7..e2f349e6478f 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/array-object.php
@@ -6,24 +6,23 @@
         clone $p['ArrayObject'],
     ],
     null,
+    [],
+    $o[0],
     [
-        'ArrayObject' => [
-            "\0" => [
-                [
-                    [
-                        1,
-                        $o[0],
-                    ],
-                    0,
-                ],
+        [
+            0,
+            [
+                1,
+                $o[0],
             ],
-        ],
-        'stdClass' => [
-            'foo' => [
-                $o[1],
+            [
+                'foo' => $o[1],
             ],
         ],
-    ],
-    $o[0],
-    []
+        -1 => [
+            0,
+            [],
+            [],
+        ],
+    ]
 );
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator-legacy.php
new file mode 100644
index 000000000000..9bdb2b366234
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator-legacy.php
@@ -0,0 +1,11 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = \Symfony\Component\VarExporter\Internal\Registry::unserialize([], [
+        'C:54:"Symfony\\Component\\VarExporter\\Tests\\FinalArrayIterator":49:{a:2:{i:0;i:123;i:1;s:21:"x:i:0;a:0:{};m:a:0:{}";}}',
+    ]),
+    null,
+    [],
+    $o[0],
+    []
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator.php
index 9bdb2b366234..7e838d1e789c 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-array-iterator.php
@@ -1,11 +1,17 @@
 <?php
 
 return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
-    $o = \Symfony\Component\VarExporter\Internal\Registry::unserialize([], [
-        'C:54:"Symfony\\Component\\VarExporter\\Tests\\FinalArrayIterator":49:{a:2:{i:0;i:123;i:1;s:21:"x:i:0;a:0:{};m:a:0:{}";}}',
-    ]),
+    $o = [
+        clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['Symfony\\Component\\VarExporter\\Tests\\FinalArrayIterator'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('Symfony\\Component\\VarExporter\\Tests\\FinalArrayIterator')),
+    ],
     null,
     [],
     $o[0],
-    []
+    [
+        [
+            0,
+            [],
+            [],
+        ],
+    ]
 );
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error-legacy.php
new file mode 100644
index 000000000000..a0202845d02e
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error-legacy.php
@@ -0,0 +1,27 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = \Symfony\Component\VarExporter\Internal\Registry::unserialize([], [
+        'O:46:"Symfony\\Component\\VarExporter\\Tests\\FinalError":1:{s:12:"'."\0".'Error'."\0".'trace";a:0:{}}',
+    ]),
+    null,
+    [
+        'TypeError' => [
+            'file' => [
+                \dirname(__DIR__).\DIRECTORY_SEPARATOR.'VarExporterTest.php',
+            ],
+            'line' => [
+                123,
+            ],
+        ],
+        'Error' => [
+            'trace' => [
+                [],
+            ],
+        ],
+    ],
+    $o[0],
+    [
+        1 => 0,
+    ]
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error.php
index dc260dc0242c..b2e729937b29 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/final-error.php
@@ -1,9 +1,9 @@
 <?php
 
 return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
-    $o = \Symfony\Component\VarExporter\Internal\Registry::unserialize([], [
-        'O:46:"Symfony\\Component\\VarExporter\\Tests\\FinalError":1:{s:12:"'."\0".'Error'."\0".'trace";a:0:{}}',
-    ]),
+    $o = [
+        (\Symfony\Component\VarExporter\Internal\Registry::$factories['Symfony\\Component\\VarExporter\\Tests\\FinalError'] ?? \Symfony\Component\VarExporter\Internal\Registry::f('Symfony\\Component\\VarExporter\\Tests\\FinalError'))(),
+    ],
     null,
     [
         'TypeError' => [
@@ -14,6 +14,11 @@
                 123,
             ],
         ],
+        'Error' => [
+            'trace' => [
+                [],
+            ],
+        ],
     ],
     $o[0],
     [
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage-legacy.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage-legacy.php
new file mode 100644
index 000000000000..5e854a4959a3
--- /dev/null
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage-legacy.php
@@ -0,0 +1,21 @@
+<?php
+
+return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
+    $o = [
+        clone (($p = &\Symfony\Component\VarExporter\Internal\Registry::$prototypes)['SplObjectStorage'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('SplObjectStorage')),
+        clone ($p['stdClass'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('stdClass')),
+    ],
+    null,
+    [
+        'SplObjectStorage' => [
+            "\0" => [
+                [
+                    $o[1],
+                    345,
+                ],
+            ],
+        ],
+    ],
+    $o[0],
+    []
+);
diff --git a/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage.php b/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage.php
index 5e854a4959a3..023a75fdcd3c 100644
--- a/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage.php
+++ b/src/Symfony/Component/VarExporter/Tests/Fixtures/spl-object-storage.php
@@ -6,16 +6,15 @@
         clone ($p['stdClass'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('stdClass')),
     ],
     null,
+    [],
+    $o[0],
     [
-        'SplObjectStorage' => [
-            "\0" => [
-                [
-                    $o[1],
-                    345,
-                ],
+        [
+            [
+                $o[1],
+                345,
             ],
+            [],
         ],
-    ],
-    $o[0],
-    []
+    ]
 );
diff --git a/src/Symfony/Component/VarExporter/Tests/VarExporterTest.php b/src/Symfony/Component/VarExporter/Tests/VarExporterTest.php
index 8a70d02be5ce..d80c2858ee91 100644
--- a/src/Symfony/Component/VarExporter/Tests/VarExporterTest.php
+++ b/src/Symfony/Component/VarExporter/Tests/VarExporterTest.php
@@ -12,7 +12,6 @@
 namespace Symfony\Component\VarExporter\Tests;
 
 use PHPUnit\Framework\TestCase;
-use PHPUnit\Framework\Warning;
 use Symfony\Component\VarDumper\Test\VarDumperTestTrait;
 use Symfony\Component\VarExporter\Internal\Registry;
 use Symfony\Component\VarExporter\VarExporter;
@@ -76,10 +75,6 @@ public function provideFailingSerialization()
      */
     public function testExport(string $testName, $value, bool $staticValueExpected = false)
     {
-        if (\PHP_VERSION_ID >= 70400 && \in_array($testName, ['spl-object-storage', 'array-object-custom', 'array-iterator', 'array-object', 'final-array-iterator'])) {
-            throw new Warning('PHP 7.4 breaks this test.');
-        }
-
         $dumpedValue = $this->getDump($value);
         $isStaticValue = true;
         $marshalledValue = VarExporter::export($value, $isStaticValue);
@@ -91,7 +86,12 @@ public function testExport(string $testName, $value, bool $staticValueExpected =
 
         $dump = "<?php\n\nreturn ".$marshalledValue.";\n";
         $dump = str_replace(var_export(__FILE__, true), "\\dirname(__DIR__).\\DIRECTORY_SEPARATOR.'VarExporterTest.php'", $dump);
-        $fixtureFile = __DIR__.'/Fixtures/'.$testName.'.php';
+
+        if (\PHP_VERSION_ID < 70400 && \in_array($testName, ['array-object', 'array-iterator', 'array-object-custom', 'spl-object-storage', 'final-array-iterator', 'final-error'], true)) {
+            $fixtureFile = __DIR__.'/Fixtures/'.$testName.'-legacy.php';
+        } else {
+            $fixtureFile = __DIR__.'/Fixtures/'.$testName.'.php';
+        }
         $this->assertStringEqualsFile($fixtureFile, $dump);
 
         if ('incomplete-class' === $testName || 'external-references' === $testName) {