diff --git a/src/things/book.ts b/src/things/book.ts
index dc9c36db..079f3e2a 100644
--- a/src/things/book.ts
+++ b/src/things/book.ts
@@ -43,6 +43,7 @@ export type SCBookCategories = 'audio'
   | 'microfilm'
   | 'musicalscore'
   | 'photo'
+  | 'physicalobject'
   | 'retro'
   | 'sensorimage'
   | 'unknown'