diff --git a/src/S3CorsManagedFileHelper.php b/src/S3CorsManagedFileHelper.php
index e58c7e3..b576825 100644
--- a/src/S3CorsManagedFileHelper.php
+++ b/src/S3CorsManagedFileHelper.php
@@ -117,7 +117,8 @@ class S3CorsManagedFileHelper {
   public static function getAcl($scheme) {
     $settings = static::getSchemeSettings($scheme);
 
-    if (array_key_exists('ACL', $settings['config']['options']['ACL'])) {
+    // config options is not required and ACL can be set to NULL to ignore x-amz-acl header.
+    if (!empty($settings['config']['options']) && array_key_exists('ACL', $settings['config']['options'])) {
       return $settings['config']['options']['ACL'];
     }