diff --git a/src/Visitor/Php/Symfony/ValidationAnnotation.php b/src/Visitor/Php/Symfony/ValidationAnnotation.php
index a8000cf..de44554 100644
--- a/src/Visitor/Php/Symfony/ValidationAnnotation.php
+++ b/src/Visitor/Php/Symfony/ValidationAnnotation.php
@@ -13,10 +13,10 @@
 
 use PhpParser\Node;
 use PhpParser\NodeVisitor;
+use Symfony\Component\Validator\Mapping\ClassMetadata;
 use Translation\Extractor\Model\SourceLocation;
 use Translation\Extractor\Visitor\Php\BasePHPVisitor;
 use Symfony\Component\Validator\Mapping\Factory\MetadataFactoryInterface;
-use Symfony\Component\Validator\MetadataFactoryInterface as LegacyMetadataFactoryInterface;
 
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
@@ -24,7 +24,7 @@
 final class ValidationAnnotation extends BasePHPVisitor implements NodeVisitor
 {
     /**
-     * @var MetadataFactoryInterface|LegacyMetadataFactoryInterface
+     * @var MetadataFactoryInterface
      */
     private $metadataFactory;
 
@@ -36,16 +36,10 @@ final class ValidationAnnotation extends BasePHPVisitor implements NodeVisitor
     /**
      * ValidationExtractor constructor.
      *
-     * @param MetadataFactoryInterface|LegacyMetadataFactoryInterface $metadataFactory
+     * @param MetadataFactoryInterface $metadataFactory
      */
-    public function __construct($metadataFactory)
+    public function __construct(MetadataFactoryInterface $metadataFactory)
     {
-        if (!(
-            $metadataFactory instanceof MetadataFactoryInterface
-            || $metadataFactory instanceof LegacyMetadataFactoryInterface
-        )) {
-            throw new \InvalidArgumentException(sprintf('%s expects an instance of MetadataFactoryInterface', get_class($this)));
-        }
         $this->metadataFactory = $metadataFactory;
     }
 
@@ -75,6 +69,7 @@ public function enterNode(Node $node)
             return;
         }
 
+        /** @var ClassMetadata $metadata */
         $metadata = $this->metadataFactory->getMetadataFor($name);
         if (!$metadata->hasConstraints() && !count($metadata->getConstrainedProperties())) {
             return;
diff --git a/tests/Functional/Visitor/Php/Symfony/ValidationAnnotationTest.php b/tests/Functional/Visitor/Php/Symfony/ValidationAnnotationTest.php
index cb4888a..8af0ba4 100644
--- a/tests/Functional/Visitor/Php/Symfony/ValidationAnnotationTest.php
+++ b/tests/Functional/Visitor/Php/Symfony/ValidationAnnotationTest.php
@@ -11,6 +11,7 @@
 
 namespace Translation\Extractor\Tests\Functional\Visitor\Php\Symfony;
 
+use Symfony\Component\Validator\Mapping\Factory\LazyLoadingMetadataFactory;
 use Translation\Extractor\Tests\Functional\Visitor\Php\BasePHPVisitorTest;
 use Translation\Extractor\Tests\Resources;
 use Translation\Extractor\Visitor\Php\Symfony\ValidationAnnotation;
@@ -24,14 +25,7 @@ final class ValidationAnnotationTest extends BasePHPVisitorTest
 {
     public function testExtractAnnotation()
     {
-        //use correct factory class depending on whether using Symfony 2 or 3
-        if (class_exists('Symfony\Component\Validator\Mapping\Factory\LazyLoadingMetadataFactory')) {
-            $metadataFactoryClass = 'Symfony\Component\Validator\Mapping\Factory\LazyLoadingMetadataFactory';
-        } else {
-            $metadataFactoryClass = 'Symfony\Component\Validator\Mapping\ClassMetadataFactory';
-        }
-
-        $factory = new $metadataFactoryClass(new AnnotationLoader(new AnnotationReader()));
+        $factory = new LazyLoadingMetadataFactory(new AnnotationLoader(new AnnotationReader()));
         $extractor = new ValidationAnnotation($factory);
         $collection = $this->getSourceLocations($extractor, Resources\Php\Symfony\ValidatorAnnotation::class);