diff --git a/src/DI/CompilerExtension.php b/src/DI/CompilerExtension.php
index 884b1ffb0..90e3ecabc 100644
--- a/src/DI/CompilerExtension.php
+++ b/src/DI/CompilerExtension.php
@@ -51,7 +51,7 @@ public function setConfig(array $config)
 	 */
 	public function getConfig(array $defaults = NULL)
 	{
-		return Config\Helpers::merge($this->config, $this->getContainerBuilder()->expand($defaults));
+		return (array) Config\Helpers::merge($this->config, $this->getContainerBuilder()->expand($defaults));
 	}