diff --git a/htdocs/core/modules/project/task/mod_task_simple.php b/htdocs/core/modules/project/task/mod_task_simple.php
index 9413ff26b9c..b0e6318ff52 100644
--- a/htdocs/core/modules/project/task/mod_task_simple.php
+++ b/htdocs/core/modules/project/task/mod_task_simple.php
@@ -72,10 +72,11 @@ class mod_task_simple extends ModeleNumRefTask
         $coyymm=''; $max='';
 
 		$posindice=8;
-		$sql = "SELECT MAX(SUBSTRING(ref FROM ".$posindice.")) as max";
-        $sql.= " FROM ".MAIN_DB_PREFIX."projet_task";
-		$sql.= " WHERE ref LIKE '".$this->prefix."____-%'";
-        $sql.= " AND entity = ".$conf->entity;
+		$sql = "SELECT MAX(SUBSTRING(task.ref FROM ".$posindice.")) as max";
+        $sql.= " FROM ".MAIN_DB_PREFIX."projet_task AS task";
+        $sql.= " INNER JOIN ".MAIN_DB_PREFIX."projet AS project ON task.fk_projet=project.rowid";
+		$sql.= " WHERE task.ref LIKE '".$this->prefix."____-%'";
+        $sql.= " AND project.entity = ".$conf->entity;
         $resql=$db->query($sql);
         if ($resql)
         {