diff --git a/module/VuFind/src/VuFind/Controller/MyResearchController.php b/module/VuFind/src/VuFind/Controller/MyResearchController.php
index 0c1f2f564ee68abcfe055438ad108627718d60a0..815f0bae5f565e04660ffea3d0987ead71c076e3 100644
--- a/module/VuFind/src/VuFind/Controller/MyResearchController.php
+++ b/module/VuFind/src/VuFind/Controller/MyResearchController.php
@@ -945,7 +945,7 @@ class MyResearchController extends AbstractBase
      */
     protected function getDriverForILSRecord($current)
     {
-        $id = $current['id'] ?? null;
+        $id = $current['id'] ?? '';
         $source = $current['source'] ?? DEFAULT_SEARCH_BACKEND;
         $record = $this->serviceLocator->get('VuFind\Record\Loader')
             ->load($id, $source, true);
diff --git a/module/VuFind/src/VuFind/ILS/Driver/MultiBackend.php b/module/VuFind/src/VuFind/ILS/Driver/MultiBackend.php
index f85770dc16e045f042375dfb747b05096650dd34..da34ab73981f7e5b9f38bd4f259a4ff605c6f08e 100644
--- a/module/VuFind/src/VuFind/ILS/Driver/MultiBackend.php
+++ b/module/VuFind/src/VuFind/ILS/Driver/MultiBackend.php
@@ -4,7 +4,7 @@
  *
  * PHP version 7
  *
- * Copyright (C) The National Library of Finland 2012-2017.
+ * Copyright (C) The National Library of Finland 2012-2018.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2,
@@ -493,7 +493,7 @@ class MultiBackend extends AbstractBase implements \Zend\Log\LoggerAwareInterfac
      */
     public function getRenewDetails($checkoutDetails)
     {
-        $source = $this->getSource($checkoutDetails['id']);
+        $source = $this->getSource($checkoutDetails['id'] ?? '');
         $driver = $this->getDriver($source);
         if ($driver) {
             $details = $driver->getRenewDetails(
@@ -883,7 +883,7 @@ class MultiBackend extends AbstractBase implements \Zend\Log\LoggerAwareInterfac
     public function getCancelHoldDetails($holdDetails)
     {
         $source = $this->getSource(
-            $holdDetails['id'] ? $holdDetails['id'] : $holdDetails['item_id']
+            $holdDetails['id'] ?? $holdDetails['item_id'] ?? ''
         );
         $driver = $this->getDriver($source);
         if ($driver) {
@@ -965,7 +965,7 @@ class MultiBackend extends AbstractBase implements \Zend\Log\LoggerAwareInterfac
      */
     public function getCancelStorageRetrievalRequestDetails($details)
     {
-        $source = $this->getSource($details['id']);
+        $source = $this->getSource($details['id'] ?? '');
         $driver = $this->getDriver($source);
         if ($driver
             && $this->methodSupported(
@@ -1172,9 +1172,7 @@ class MultiBackend extends AbstractBase implements \Zend\Log\LoggerAwareInterfac
      */
     public function getCancelILLRequestDetails($details)
     {
-        $source = $this->getSource(
-            $details['id'] ? $details['id'] : $details['item_id']
-        );
+        $source = $this->getSource($details['id'] ?? $details['item_id'] ?? '');
         $driver = $this->getDriver($source);
         if ($driver
             && $this->methodSupported(