diff --git a/src/Controller/WarrantyController.php b/src/Controller/WarrantyController.php
index 1c41ccfa..d7ab6eb7 100644
--- a/src/Controller/WarrantyController.php
+++ b/src/Controller/WarrantyController.php
@@ -164,7 +164,7 @@ class WarrantyController extends Controller
         $date_expire = DateTime::createFromFormat('d M Y', $req->request->get('date_expire'));
 
         // get serial. Set to null if empty
-        if (empty($req->request->get('serial')))
+        if (empty(trim($req->request->get('serial'))))
             $obj->setSerial();
         else
             $obj->setSerial($req->request->get('serial'));
@@ -331,7 +331,7 @@ class WarrantyController extends Controller
         $date_expire = DateTime::createFromFormat('d M Y', $req->request->get('date_expire'));
 
         // get serial. Set to null if empty
-        if (empty($req->request->get('serial')))
+        if (empty(trim($req->request->get('serial'))))
             $obj->setSerial();
         else
             $obj->setSerial($req->request->get('serial'));