diff --git a/module/VuFind/src/VuFind/ILS/Driver/Aleph.php b/module/VuFind/src/VuFind/ILS/Driver/Aleph.php
index 52abb9f9f17d180761af5ba2eec05b4c2547ddf7..6daf4f34474cd473de2366538bbd26dd5913e1a6 100644
--- a/module/VuFind/src/VuFind/ILS/Driver/Aleph.php
+++ b/module/VuFind/src/VuFind/ILS/Driver/Aleph.php
@@ -575,10 +575,17 @@ class Aleph extends AbstractBase implements \Zend\Log\LoggerAwareInterface,
     protected function parseId($id)
     {
         if (count($this->bib) == 1) {
-            return [$this->bib[0], $id];
+            $retval = [$this->bib[0], $id];
         } else {
-            return explode('-', $id);
+            $retval = explode('-', $id);
         }
+        if (count($retval) != 2) {
+            throw new \Exception("The resulting array has incorrect size");
+        }
+        if (!in_array($retval[0], $this->bib)) {
+            throw new \Exception("The resulting array contains unknown library ID");
+        }
+        return $retval;
     }
 
     /**