diff --git a/module/VuFind/src/VuFind/Controller/BrowseController.php b/module/VuFind/src/VuFind/Controller/BrowseController.php
index 0223998b1477f63b7076faeb1520480b274afffd..c1dfaef0a20550b9b0e68fddaa9348d32c62c9c9 100644
--- a/module/VuFind/src/VuFind/Controller/BrowseController.php
+++ b/module/VuFind/src/VuFind/Controller/BrowseController.php
@@ -380,7 +380,7 @@ class BrowseController extends AbstractBase
                     $this->params()->fromQuery('findby')
                 )
             );
-            foreach ($secondaryList as $index=>$item) {
+            foreach (array_keys($secondaryList) as $index) {
                 $secondaryList[$index]['value'] .=
                     ' AND dewey-hundreds:'
                     . $this->params()->fromQuery('findby');