diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
index 1717426161d49..069d2e3935f62 100644
--- a/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
@@ -339,7 +339,7 @@ public function denormalize(mixed $data, string $type, string $format = null, ar
             $normalizedData = $this->removeNestedValue($serializedPath->getElements(), $normalizedData);
         }
 
-        $normalizedData = array_merge($normalizedData, $nestedData);
+        $normalizedData = $normalizedData + $nestedData;
 
         $object = $this->instantiateObject($normalizedData, $mappedClass, $context, new \ReflectionClass($mappedClass), $allowedAttributes, $format);
         $resolvedClass = ($this->objectClassResolver)($object);
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php
index 61345a414eea4..8eb77718c4ac9 100644
--- a/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php
+++ b/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php
@@ -787,6 +787,32 @@ classMetadataFactory: new ClassMetadataFactory(new AnnotationLoader()),
         $normalized = $serializer->normalize(new DummyWithEnumUnion(EnumB::B));
         $this->assertEquals(new DummyWithEnumUnion(EnumB::B), $serializer->denormalize($normalized, DummyWithEnumUnion::class));
     }
+
+    public function testDenormalizeWithNumberAsSerializedNameAndNoArrayReindex()
+    {
+        $normalizer = new AbstractObjectNormalizerWithMetadata();
+
+        $data = [
+            '1' => 'foo',
+            '99' => 'baz',
+        ];
+
+        $obj = new class() {
+            /**
+             * @SerializedName("1")
+             */
+            public $foo;
+
+            /**
+             * @SerializedName("99")
+             */
+            public $baz;
+        };
+
+        $test = $normalizer->denormalize($data, $obj::class);
+        $this->assertSame('foo', $test->foo);
+        $this->assertSame('baz', $test->baz);
+    }
 }
 
 class AbstractObjectNormalizerDummy extends AbstractObjectNormalizer