diff --git a/module/VuFind/src/VuFind/ILS/Driver/VoyagerRestful.php b/module/VuFind/src/VuFind/ILS/Driver/VoyagerRestful.php
index ff19d6ea14ebc2d05bacdc4e30ec324a4c9b7ccd..ab777a252ef722cb885c55f356fea9d3ad1052e2 100644
--- a/module/VuFind/src/VuFind/ILS/Driver/VoyagerRestful.php
+++ b/module/VuFind/src/VuFind/ILS/Driver/VoyagerRestful.php
@@ -330,7 +330,7 @@ class VoyagerRestful extends Voyager implements \VuFindHttp\HttpServiceAwareInte
      *
      * @return string
      */
-    protected function getCacheKey($key)
+    protected function getCacheKey($key = null)
     {
         // Override the base class formatting with Voyager-specific details
         // to ensure proper caching in a MultiBackend environment.