diff --git a/htdocs/projet/class/project.class.php b/htdocs/projet/class/project.class.php
index 02298c196ca..e6c718c655f 100644
--- a/htdocs/projet/class/project.class.php
+++ b/htdocs/projet/class/project.class.php
@@ -1146,6 +1146,8 @@ class Project extends CommonObject
 			//Duplicate task
 			if ($clone_task)
 			{
+				require_once DOL_DOCUMENT_ROOT . '/projet/class/task.class.php';
+
 				$taskstatic = new Task($this->db);
 
 				// Security check