diff --git a/src/Symfony/Component/Serializer/Encoder/YamlEncoder.php b/src/Symfony/Component/Serializer/Encoder/YamlEncoder.php
index 41ac04f209105..3ac1af679a4a1 100644
--- a/src/Symfony/Component/Serializer/Encoder/YamlEncoder.php
+++ b/src/Symfony/Component/Serializer/Encoder/YamlEncoder.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Serializer\Encoder;
 
+use Symfony\Component\Serializer\Exception\RuntimeException;
 use Symfony\Component\Yaml\Dumper;
 use Symfony\Component\Yaml\Parser;
 
@@ -29,6 +30,10 @@ class YamlEncoder implements EncoderInterface, DecoderInterface
 
     public function __construct(Dumper $dumper = null, Parser $parser = null, array $defaultContext = array())
     {
+        if (!class_exists(Dumper::class)) {
+            throw new RuntimeException('The YamlEncoder class requires the "Yaml" component. Install "symfony/yaml" to use it.');
+        }
+
         $this->dumper = $dumper ?: new Dumper();
         $this->parser = $parser ?: new Parser();
         $this->defaultContext = array_merge($this->defaultContext, $defaultContext);
diff --git a/src/Symfony/Component/Serializer/Normalizer/DataUriNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/DataUriNormalizer.php
index 9e5af130d03b7..121d3425f74f1 100644
--- a/src/Symfony/Component/Serializer/Normalizer/DataUriNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/DataUriNormalizer.php
@@ -110,7 +110,7 @@ public function supportsDenormalization($data, $type, $format = null)
         $supportedTypes = array(
             \SplFileInfo::class => true,
             \SplFileObject::class => true,
-            'Symfony\Component\HttpFoundation\File\File' => true,
+            File::class => true,
         );
 
         return isset($supportedTypes[$type]);