diff --git a/src/services/WorkPeriodProcessorService.js b/src/services/WorkPeriodProcessorService.js
index 770f774..8350056 100644
--- a/src/services/WorkPeriodProcessorService.js
+++ b/src/services/WorkPeriodProcessorService.js
@@ -47,6 +47,7 @@ processCreate.schema = {
     originator: Joi.string().required(),
     timestamp: Joi.date().required(),
     'mime-type': Joi.string().required(),
+    key: Joi.string().allow(null),
     payload: Joi.object().keys({
       id: Joi.string().uuid().required(),
       resourceBookingId: Joi.string().uuid().required(),