diff --git a/src/Symfony/Component/Debug/ErrorHandler.php b/src/Symfony/Component/Debug/ErrorHandler.php
index 7e8bbc55421c2..d0566ae18ea7b 100644
--- a/src/Symfony/Component/Debug/ErrorHandler.php
+++ b/src/Symfony/Component/Debug/ErrorHandler.php
@@ -125,6 +125,9 @@ function ($row) {
             if (!class_exists('Symfony\Component\Debug\Exception\ContextErrorException')) {
                 require __DIR__.'/Exception/ContextErrorException.php';
             }
+            if (!class_exists('Symfony\Component\Debug\Exception\FlattenException')) {
+                require __DIR__.'/Exception/FlattenException.php';
+            }
 
             if (PHP_VERSION_ID < 50400 && isset($context['GLOBALS']) && is_array($context)) {
                 unset($context['GLOBALS']);