diff --git a/src/CollectionExtension.php b/src/CollectionExtension.php
index 092cd25..4585a8e 100644
--- a/src/CollectionExtension.php
+++ b/src/CollectionExtension.php
@@ -68,7 +68,7 @@ class CollectionExtension
         };
     }
 
-    public function setDefaultCustomCallbacks()
+    protected function setDefaultCustomCallbacks()
     {
         return function () {
             if (property_exists($this, 'customCallbacks')) {