diff --git a/htdocs/core/class/html.form.class.php b/htdocs/core/class/html.form.class.php
index 7d74276ce90..99dd80a8b2d 100644
--- a/htdocs/core/class/html.form.class.php
+++ b/htdocs/core/class/html.form.class.php
@@ -3890,9 +3890,10 @@ class Form
 	 *      @param	string	$selected       Preselected Unit ID
 	 *      @param  string	$htmlname       Select name
 	 *      @param	int		$showempty		Add a nempty line
+	 *      @param  string  $unit_type      Restrict to one given unit type
 	 * 		@return	string                  HTML select
 	 */
-	public function selectUnits($selected = '', $htmlname = 'units', $showempty = 0, $unit_type = false)
+	public function selectUnits($selected = '', $htmlname = 'units', $showempty = 0, $unit_type = '')
 	{
 		global $langs;
 
@@ -3902,8 +3903,8 @@ class Form
 
 		$sql = 'SELECT rowid, label, code from '.MAIN_DB_PREFIX.'c_units';
 		$sql .= ' WHERE active > 0';
-		if (!empty($unit_type)){
-			$sql .= ' AND unit_type = "'.$this->db->escape($unit_type).'" ';
+		if (!empty($unit_type)) {
+			$sql .= " AND unit_type = '".$this->db->escape($unit_type)."'";
 		}
 
 		$resql = $this->db->query($sql);