diff --git a/htdocs/projet/class/project.class.php b/htdocs/projet/class/project.class.php
index cbed549ac29..7e64f9a5011 100644
--- a/htdocs/projet/class/project.class.php
+++ b/htdocs/projet/class/project.class.php
@@ -1691,7 +1691,8 @@ class Project extends CommonObject
 			$sql.= " WHERE id=".$elementSelectId;
 		}else
 		{
-			$sql.= sprintf(" SET %s=NULL WHERE rowid=%s", $projectfield, $elementSelectId);
+			$sql.= " SET ".$projectfield."=NULL";
+			$sql.= " WHERE rowid=".$elementSelectId;
 		}
 
 		dol_syslog(get_class($this)."::remove_element", LOG_DEBUG);