diff --git a/htdocs/bom/class/api_boms.class.php b/htdocs/bom/class/api_boms.class.php
index 52e6fe90501bd..2147f7be1ba9c 100644
--- a/htdocs/bom/class/api_boms.class.php
+++ b/htdocs/bom/class/api_boms.class.php
@@ -546,7 +546,7 @@ private function _validate($data)
 	 *
 	 * @return void
 	 */
-	private function checkRefNumbering(): void
+	private function checkRefNumbering()
 	{
 		$ref = substr($this->bom->ref, 1, 4);
 		if ($this->bom->status > 0 && $ref == 'PROV') {