diff --git a/module/VuFind/src/VuFind/DoiLinker/BrowZine.php b/module/VuFind/src/VuFind/DoiLinker/BrowZine.php
index 5fa9de39bbbc5928b98d91b76518d8f85b30f63b..0c12d20aa70b25c91c000b5c2dea7914e35d2dd0 100644
--- a/module/VuFind/src/VuFind/DoiLinker/BrowZine.php
+++ b/module/VuFind/src/VuFind/DoiLinker/BrowZine.php
@@ -77,7 +77,7 @@ class BrowZine implements DoiLinkerInterface, TranslatorAwareInterface
      *
      * @return bool
      */
-    protected function arrayKeyAvailable(string $key, array $data): bool
+    protected function arrayKeyAvailable(string $key, ?array $data): bool
     {
         if (empty($data[$key])) {
             return false;