diff --git a/classes/Autoload.php b/classes/Autoload.php
index ad4f3c49f..96bb8f54d 100644
--- a/classes/Autoload.php
+++ b/classes/Autoload.php
@@ -133,7 +133,9 @@ class Autoload
 
 		// Write classes index on disc to cache it
 		$filename = $this->root_dir.Autoload::INDEX_FILE;
-		if ((file_exists($filename) && is_writable($filename)) || is_writable(dirname($filename)))
+		if ((file_exists($filename) && !is_writable($filename)) || !is_writable(dirname($filename)))
+			throw new PrestaShopException($filename.' is not writable, please give write permissions (chmod 666) on this file.');
+		else
 		{
 			// Let's write index content in cache file
 			// In order to be sure that this file is correctly written, a check is done on the file content
@@ -157,8 +159,6 @@ class Autoload
 				throw new PrestaShopException('Your file '.$filename.' is corrupted. Please remove this file, a new one will be regenerated automatically');
 			}
 		}
-		else
-			throw new PrestaShopException($filename.' is not writable!');
 
 		$this->index = $classes;
 	}