--- /dev/null
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Definition\Exception;
+
+/**
+ * This exception is thrown whenever the key of an array is not unique. This can
+ * only be the case if the configuration is coming from an XML file.
+ *
+ * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ */
+class DuplicateKeyException extends InvalidConfigurationException
+{
+}