diff --git a/src/Symfony/Component/Validator/CHANGELOG.md b/src/Symfony/Component/Validator/CHANGELOG.md
index 740e23b09051e..b5b623a301d6b 100644
--- a/src/Symfony/Component/Validator/CHANGELOG.md
+++ b/src/Symfony/Component/Validator/CHANGELOG.md
@@ -11,6 +11,7 @@ CHANGELOG
    the `Url::CHECK_DNS_TYPE_*` constants values and will throw an exception in Symfony 4.0
  * added min/max amount of pixels check to `Image` constraint via `minPixels` and `maxPixels`
  * added a new "propertyPath" option to comparison constraints in order to get the value to compare from an array or object
+ * added magic method `__isset()` to `File` constraint class
 
 3.3.0
 -----
diff --git a/src/Symfony/Component/Validator/Constraints/File.php b/src/Symfony/Component/Validator/Constraints/File.php
index 4d4c68d7fd9fb..5cc3a7313f7a5 100644
--- a/src/Symfony/Component/Validator/Constraints/File.php
+++ b/src/Symfony/Component/Validator/Constraints/File.php
@@ -88,6 +88,15 @@ public function __get($option)
         return parent::__get($option);
     }
 
+    public function __isset($option)
+    {
+        if ('maxSize' === $option) {
+            return true;
+        }
+
+        return parent::__isset($option);
+    }
+
     private function normalizeBinaryFormat($maxSize)
     {
         $factors = array(