diff --git a/bootstrap.php b/bootstrap.php
index b303616ff224faee61b25493bf193011e3e96d9f..c37e3f6f04d6080f31e1c4ed15f0e4313e6bb2fd 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -215,10 +215,10 @@ class Bootstrap {
             }
             define('LATIN1_UC_CHARS', 'ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝ');
             define('LATIN1_LC_CHARS', 'àáâãäåæçèéêëìíîïðñòóôõöøùúûüý');
-            function mb_strtoupper($a) {
+            function mb_strtoupper($str) {
                 return strtoupper(strtr($str, LATIN1_LC_CHARS, LATIN1_UC_CHARS));
             }
-            function mb_strtolower($a) {
+            function mb_strtolower($str) {
                 return strtolower(strtr($str, LATIN1_UC_CHARS, LATIN1_LC_CHARS));
             }
             define('MB_CASE_LOWER', 1);