diff --git a/src/clients/BaseClient.php b/src/clients/BaseClient.php
index ff3edd1..64dcea6 100644
--- a/src/clients/BaseClient.php
+++ b/src/clients/BaseClient.php
@@ -71,7 +71,7 @@ public function setLogger(LoggerInterface $logger){
      * @return array
      */
     protected function getMaskedParams($paramsToMask){
-        array_walk_recursive($paramsToMask, function(&$value, &$key) {
+        array_walk_recursive($paramsToMask, function(&$value, $key) {
             if(in_array($key, array('pan', 'cvv', 'holder', 'expiration_month', 'expiration_year'))){
                 $value = str_repeat('*', strlen($value));
             }