diff --git a/types/packaging.d.ts b/types/packaging.d.ts
index 7151956..1d40aae 100644
--- a/types/packaging.d.ts
+++ b/types/packaging.d.ts
@@ -36,7 +36,8 @@ export interface PackagingSpineItem {
 export interface PackagingManifestItem {
   href: string,
   type: string,
-  properties: Array<string>
+  properties: Array<string>,
+  fallback: string
 }
 
 export interface PackagingManifestObject {