diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 2a5324da295..3fdc72816d1 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -518,6 +518,7 @@ class Product extends CommonObject
 					$newdir = $conf->product->dir_output . "/" . dol_sanitizeFileName($this->ref);
 					if (file_exists($olddir))
 					{
+						include_once DOL_DOCUMENT_ROOT . '/core/lib/files.lib.php';
 						$res=@dol_move($olddir, $newdir);
 						if (! $res)
 						{