diff --git a/src/Bridges/MailDI/MailExtension.php b/src/Bridges/MailDI/MailExtension.php
index fdef305..a209ef6 100644
--- a/src/Bridges/MailDI/MailExtension.php
+++ b/src/Bridges/MailDI/MailExtension.php
@@ -45,7 +45,7 @@ public function getConfigSchema(): Nette\Schema\Schema
 	}
 
 
-	public function loadConfiguration()
+	public function loadConfiguration(): void
 	{
 		$builder = $this->getContainerBuilder();