diff --git a/lib/AlmaClient/AlmaClient.class.php b/lib/AlmaClient/AlmaClient.class.php
index d1800cb..060bcf0 100644
--- a/lib/AlmaClient/AlmaClient.class.php
+++ b/lib/AlmaClient/AlmaClient.class.php
@@ -438,7 +438,7 @@ public function add_reservation($borr_card, $pin_code, $reservation) {
     $params = array(
       'borrCard' => $borr_card,
       'pinCode' => $pin_code,
-      'reservable' => $reservation['id'],
+      'reservable' => rawurlencode($reservation['id']),
       'reservationPickUpBranch' => $reservation['pickup_branch'],
       'reservationValidFrom' => $reservation['valid_from'],
       'reservationValidTo' => $reservation['valid_to'],