diff --git a/src/Reader/PhpReader.php b/src/Reader/PhpReader.php
index a090011..ad926c2 100644
--- a/src/Reader/PhpReader.php
+++ b/src/Reader/PhpReader.php
@@ -41,7 +41,7 @@ class PhpReader implements ReaderInterface {
         $path = $this->pathList[0];
 
         if ( ! file_exists($path) ) {
-            mkdir($path, '755', true);
+            mkdir($path, 0755, true);
         }
 
         return (bool) file_put_contents($path . DIRECTORY_SEPARATOR . "$filepath.{$this->accept[0]}", "<?php return " . var_export($content, true) . ";");