diff --git a/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php b/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php
index a091cfab69a07..4339d3fee2b4e 100644
--- a/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php
+++ b/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php
@@ -154,10 +154,13 @@ public function decode($data, $format, array $context = [])
         $rootNode = null;
         $decoderIgnoredNodeTypes = $context[self::DECODER_IGNORED_NODE_TYPES] ?? $this->defaultContext[self::DECODER_IGNORED_NODE_TYPES];
         foreach ($dom->childNodes as $child) {
+            if (\in_array($child->nodeType, $decoderIgnoredNodeTypes, true)) {
+                continue;
+            }
             if (\XML_DOCUMENT_TYPE_NODE === $child->nodeType) {
                 throw new NotEncodableValueException('Document types are not allowed.');
             }
-            if (!$rootNode && !\in_array($child->nodeType, $decoderIgnoredNodeTypes, true)) {
+            if (!$rootNode) {
                 $rootNode = $child;
             }
         }
diff --git a/src/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php b/src/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php
index 0752021605b72..2d35bf43be736 100644
--- a/src/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php
+++ b/src/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php
@@ -587,6 +587,33 @@ public function testDecodeIgnoreComments()
         $this->assertEquals($expected, $this->encoder->decode($source, 'xml'));
     }
 
+    public function testDecodeIgnoreDocumentType()
+    {
+        $source = <<<'XML'
+<?xml version="1.0"?>
+<!DOCTYPE people>
+<people>
+    <person>
+        <firstname>Benjamin</firstname>
+        <lastname>Alexandre</lastname>
+    </person>
+    <person>
+        <firstname>Damien</firstname>
+        <lastname>Clay</lastname>
+    </person>
+</people>
+XML;
+        $expected = ['person' => [
+          ['firstname' => 'Benjamin', 'lastname' => 'Alexandre'],
+          ['firstname' => 'Damien', 'lastname' => 'Clay'],
+        ]];
+        $this->assertEquals($expected, $this->encoder->decode(
+            $source,
+            'xml',
+            [XmlEncoder::DECODER_IGNORED_NODE_TYPES => [\XML_DOCUMENT_TYPE_NODE]]
+        ));
+    }
+
     public function testDecodePreserveComments()
     {
         $this->doTestDecodePreserveComments();