diff --git a/src/Extender.php b/src/Extender.php
index 1f77feb..b02117c 100644
--- a/src/Extender.php
+++ b/src/Extender.php
@@ -13,7 +13,7 @@
 // Explicitly require ExtenderManager here.
 // When this package is uninstalled, ExtenderManager needs to be available any
 // time this class is available.
-require_once 'ExtenderManager.php';
+require_once __DIR__ . '/ExtenderManager.php';
 
 class Extender implements PluginInterface, EventSubscriberInterface
 {