diff --git a/swh/scheduler/celery_backend/config.py b/swh/scheduler/celery_backend/config.py
--- a/swh/scheduler/celery_backend/config.py
+++ b/swh/scheduler/celery_backend/config.py
@@ -313,7 +313,7 @@
     # A string identifying the default serialization method to use.
     # Can be pickle (default), json, yaml, msgpack or any custom serialization
     # methods that have been registered with kombu.serialization.registry
-    accept_content=["msgpack", "json"],
+    accept_content=["msgpack", "application/x-msgpack", "json"],
     # If True the task will report its status as “started”
     # when the task is executed by a worker.
     task_track_started=True,