diff --git a/htdocs/core/class/html.form.class.php b/htdocs/core/class/html.form.class.php
index c4b025878c5..aa1f79cfb11 100755
--- a/htdocs/core/class/html.form.class.php
+++ b/htdocs/core/class/html.form.class.php
@@ -2666,7 +2666,7 @@ class Form
 	 *
 	 * @return    string                     HTML select
 	 */
-	function load_situation_invoices($selected = '', $socid)
+	function load_situation_invoices($selected = '', $socid = '')
 	{
 		global $langs;