diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
index b0a1f3218b830..7f86ed8d786e4 100644
--- a/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
@@ -296,7 +296,7 @@ protected function isAllowedAttribute(object|string $classOrObject, string $attr
      * Normalizes the given data to an array. It's particularly useful during
      * the denormalization process.
      */
-    protected function prepareForDenormalization(object|array|null $data): array
+    protected function prepareForDenormalization(mixed $data): array
     {
         return (array) $data;
     }
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractNormalizerTest.php
index 074e44e7adea8..5d7a42dba6b7a 100644
--- a/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractNormalizerTest.php
+++ b/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractNormalizerTest.php
@@ -5,6 +5,7 @@
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\PropertyInfo\Extractor\PhpDocExtractor;
+use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
 use Symfony\Component\Serializer\Encoder\JsonEncoder;
 use Symfony\Component\Serializer\Mapping\AttributeMetadata;
 use Symfony\Component\Serializer\Mapping\ClassMetadata;
@@ -217,4 +218,15 @@ public function testIgnore()
 
         $this->assertSame([], $normalizer->normalize($dummy));
     }
+
+    public function testDenormalizeRecursiveWithObjectAttributeWithStringValue()
+    {
+        $extractor = new ReflectionExtractor();
+        $normalizer = new ObjectNormalizer(null, null, null, $extractor);
+        $serializer = new Serializer([$normalizer]);
+
+        $obj = $serializer->denormalize(['inner' => 'foo'], ObjectOuter::class);
+
+        $this->assertInstanceOf(ObjectInner::class, $obj->getInner());
+    }
 }