diff --git a/kiri-engine/Pool/Pool.php b/kiri-engine/Pool/Pool.php
index c34f76d9..fb6375b8 100644
--- a/kiri-engine/Pool/Pool.php
+++ b/kiri-engine/Pool/Pool.php
@@ -226,9 +226,9 @@ class Pool extends Component
 
 	/**
 	 * @param string $name
-	 * @return mixed
+	 * @return int
 	 */
-	public function size(string $name): mixed
+	public function size(string $name): int
 	{
 		if (!isset(static::$_connections[$name])) {
 			return 0;