diff --git a/src/IDF/Conf.php b/src/IDF/Conf.php
index 0d57536..ea5b4a4 100644
--- a/src/IDF/Conf.php
+++ b/src/IDF/Conf.php
@@ -122,7 +122,7 @@ class IDF_Conf extends Pluf_Model
     function delVal($key, $initcache=true)
     {
         $gconf = new IDF_Conf();
-        $sql = new Pluf_SQL('vkey=%s AND project=%s', array($key, $this->_project));
+        $sql = new Pluf_SQL('vkey=%s AND project=%s', array($key, $this->_project->id));
         foreach ($gconf->getList(array('filter' => $sql->gen())) as $c) {
             $c->delete();
         }