diff --git a/src/services/processorService.js b/src/services/processorService.js
index 685d95b..45facb6 100644
--- a/src/services/processorService.js
+++ b/src/services/processorService.js
@@ -120,6 +120,7 @@ processUpdate.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().required(),
       legacyId: Joi.number().integer().positive(),