diff --git a/src/Symfony/Component/PropertyInfo/Tests/Fixtures/NullExtractor.php b/src/Symfony/Component/PropertyInfo/Tests/Fixtures/NullExtractor.php
index c6a1785f49..e9fa800133 100644
--- a/src/Symfony/Component/PropertyInfo/Tests/Fixtures/NullExtractor.php
+++ b/src/Symfony/Component/PropertyInfo/Tests/Fixtures/NullExtractor.php
@@ -30,6 +30,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     {
         $this->assertIsString($class);
         $this->assertIsString($property);
+
+        return null;
     }
 
     /**
@@ -39,6 +41,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     {
         $this->assertIsString($class);
         $this->assertIsString($property);
+
+        return null;
     }
 
     /**
@@ -48,6 +52,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     {
         $this->assertIsString($class);
         $this->assertIsString($property);
+
+        return null;
     }
 
     /**
@@ -57,6 +63,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     {
         $this->assertIsString($class);
         $this->assertIsString($property);
+
+        return null;
     }
 
     /**
@@ -66,6 +74,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     {
         $this->assertIsString($class);
         $this->assertIsString($property);
+
+        return null;
     }
 
     /**
@@ -74,6 +84,8 @@ class NullExtractor implements PropertyListExtractorInterface, PropertyDescripti
     public function getProperties($class, array $context = [])
     {
         $this->assertIsString($class);
+
+        return null;
     }
 
     private function assertIsString($string)