diff --git a/modules/core/lib/ACL.php b/modules/core/lib/ACL.php
index 1bd1ad8dc8c691309c13a7fbdfcb3fb51598ea90..cf8127ed35016e7a75988225207629d860c5d59e 100644
--- a/modules/core/lib/ACL.php
+++ b/modules/core/lib/ACL.php
@@ -56,7 +56,7 @@ class sspmod_core_ACL {
 	private static function getById($id) {
 		assert('is_string($id)');
 
-		$config = SimpleSAML_Configuration::getConfig('acl.php');
+		$config = SimpleSAML_Configuration::getOptionalConfig('acl.php');
 		if (!$config->hasValue($id)) {
 			throw new SimpleSAML_Error_Exception('No ACL with id ' . var_export($id, TRUE) . ' in config/acl.php.');
 		}