diff --git a/src/Config/Loader/FileLoader/Json.php b/src/Config/Loader/FileLoader/Json.php
index 2fda757..3643e57 100644
--- a/src/Config/Loader/FileLoader/Json.php
+++ b/src/Config/Loader/FileLoader/Json.php
@@ -51,7 +51,7 @@ private function isJson($string)
     {
         return (
             !empty($string) &&
-            ($string{0} === '[' || $string{0} === '{')
+            ($string[0] === '[' || $string[0] === '{')
         );
     }