diff --git a/lib/PayPal/Common/ReflectionUtil.php b/lib/PayPal/Common/ReflectionUtil.php
index f7b397a..a2f532e 100644
--- a/lib/PayPal/Common/ReflectionUtil.php
+++ b/lib/PayPal/Common/ReflectionUtil.php
@@ -150,6 +150,6 @@ class ReflectionUtil
     {
         return method_exists($class, "get" . ucfirst($propertyName)) ?
             "get" . ucfirst($propertyName) :
-            "get" . preg_replace_callback("/([_\-\s]?([a-z0-9]+))/", "self::replace_callback", $propertyName);
+            "get" . preg_replace_callback("/([_\-\s]?([a-z0-9]+))/", self::class . "::replace_callback", $propertyName);
     }
 }