diff --git a/lib/resources.js b/lib/resources.js
index 462ae779..3c9cccf6 100644
--- a/lib/resources.js
+++ b/lib/resources.js
@@ -46,6 +46,10 @@ const SORT_FIELDS = {
     initialDirection: 'asc',
     field: 'creator_sort'
   },
+  callnumber: {
+    initialDirection: 'asc',
+    field: 'shelfMark.keywordLowercased'
+  },
   relevance: {}
 }